Method for manufacturing a multi-wavelength integrated semiconductor laser

Abstract

Disclosed is a manufacturing method of a multi-wavelength integrated semiconductor laser capable of making the heights of active layers of a plurality of semiconductor laser sections responsible for laser oscillation in different wavelength bands uniform. The manufacturing method of the multi-wavelength integrated semiconductor laser includes the following steps: a step of epitaxially growing a semiconductor layer on a semiconductor substrate; a step of etching the semiconductor layer to form a first groove and a second groove at the same time; a step of forming a first semiconductor laser section by epitaxially growing at least a first active layer selectively in the first groove; a step of forming a second semiconductor laser section by epitaxially growing at least a second active layer selectively in the second groove; and a step of performing dry etching to form a mesa structure of the first semiconductor laser section and the second semiconductor laser section on the basis of masking a part of an upper surface of the first semiconductor laser section and an upper surface of the second semiconductor laser section with an insulating film.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a multi-wavelength integrated semiconductor laser having multiple semiconductor lasers each responsible for laser oscillation in a different wavelength band. Background Technology

[0002] The demand for multi-wavelength integrated semiconductor lasers is for further increases in speed, functionality, and cost. In the technology disclosed in Patent Document 1, a ridge structure for a first semiconductor laser section is first formed on a semiconductor substrate. Next, a ridge structure for a second semiconductor laser section having an oscillation band different from that of the first semiconductor laser section is formed. By sequentially forming multiple semiconductor laser sections with different oscillation bands, high integration can be achieved.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2004-207588

[0004] In multi-wavelength integrated semiconductor lasers, it is desirable for the wavelength characteristics to remain unchanged. Therefore, high uniformity of the active layer in each semiconductor laser section is desirable.

[0005] In the prior art, a semiconductor layer for a first semiconductor laser portion is first epitaxially grown. Then, etching is performed to form a ridge structure for the first semiconductor laser portion, exposing the semiconductor substrate except for the area of ​​the ridge structure. Next, a semiconductor layer for a second semiconductor laser portion is epitaxially grown, covering the ridge structure of the first semiconductor laser portion. Then, a photoresist is used to mask the formation of the second semiconductor laser portion. Finally, etching is performed to form the ridge structure of the second semiconductor laser portion.

[0006] In the prior art, excessive etching during the formation of the ridge structure of the first semiconductor laser section can etch into the semiconductor substrate. This causes the surface of the semiconductor substrate from which the epitaxial growth of the semiconductor layer of the second semiconductor laser section begins to differ from that of the first semiconductor laser section. Consequently, the height of the active layer is inconsistent between the first and second semiconductor laser sections. Summary of the Invention

[0007] In order to solve the above-mentioned problems, this disclosure aims to provide a method for manufacturing a multi-wavelength integrated semiconductor laser that enables the active layers of multiple semiconductor laser sections, each responsible for laser oscillation in different wavelength bands, to be highly consistent.

[0008] The preferred embodiment of this disclosure is a method for manufacturing a multi-wavelength integrated semiconductor laser, characterized by comprising the following steps:

[0009] The process of epitaxially growing a semiconductor layer on a semiconductor substrate;

[0010] The process of etching the semiconductor layer to simultaneously form the first trench and the second trench;

[0011] The process of forming a first semiconductor laser part by epitaxially growing at least a first active layer in the first trench, based on masking the inner side of the second trench and the upper surface of the semiconductor layer with a first insulating film;

[0012] After removing the first insulating film, and masking the upper surface of the first semiconductor laser portion and the upper surface of the semiconductor layer with a second insulating film, a second active layer is epitaxially grown in the second trench to form a second semiconductor laser portion; and

[0013] After removing the second insulating film, and masking a portion of the upper surface of the first semiconductor laser portion and the upper surface of the second semiconductor laser portion with a third insulating film, dry etching is performed on the first semiconductor laser portion, the second semiconductor laser portion, and the semiconductor layer to form the mesa structure of the first semiconductor laser portion and the mesa structure of the second semiconductor laser portion.

[0014] In this disclosure, a first trench and a second trench are simultaneously formed by etching a semiconductor layer formed on a semiconductor substrate. A first active layer is selectively epitaxially grown at least inside the first trench to form a first semiconductor laser portion, and a second active layer is selectively epitaxially grown at least inside the second trench to form a second semiconductor laser portion. Since the semiconductor layers of the first and second semiconductor laser portions can be epitaxially grown on the semiconductor substrate from the surface where the same etching has been performed, the heights of the first and second active layers can be made identical. Attached Figure Description

[0015] Figure 1 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0016] Figure 2 yes Figure 1 A sectional view.

[0017] Figure 3 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0018] Figure 4 yes Figure 3 A sectional view.

[0019] Figure 5 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0020] Figure 6 yes Figure 5 A sectional view.

[0021] Figure 7 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0022] Figure 8 yes Figure 7 A sectional view.

[0023] Figure 9 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0024] Figure 10 yes Figure 9 A sectional view.

[0025] Figure 11 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0026] Figure 12 yes Figure 11 A sectional view.

[0027] Figure 13 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0028] Figure 14 yes Figure 13 A sectional view.

[0029] Figure 15 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0030] Figure 16 yes Figure 15 A sectional view.

[0031] Figure 17 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0032] Figure 18 yes Figure 17 A sectional view.

[0033] Figure 19 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0034] Figure 20 yes Figure 19 A sectional view.

[0035] Figure 21 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0036] Figure 22 yes Figure 21 AA sectional view.

[0037] Figure 23 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0038] Figure 24 yes Figure 23 AA sectional view.

[0039] Figure 25 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0040] Figure 26 yes Figure 25 AA sectional view.

[0041] Figure 27 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0042] Figure 28 yes Figure 27 AA sectional view.

[0043] Figure 29 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0044] Figure 30 yes Figure 29 A sectional view.

[0045] Figure 31 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0046] Figure 32 yes Figure 31 A sectional view.

[0047] Figure 33 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 1.

[0048] Figure 34 yes Figure 33 A sectional view.

[0049] Figure 35 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 2.

[0050] Figure 36 yes Figure 35 A sectional view.

[0051] Figure 37 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 2.

[0052] Figure 38 yes Figure 37 A sectional view.

[0053] Figure 39 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 2.

[0054] Figure 40 yes Figure 39 A sectional view.

[0055] Figure 41 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 2.

[0056] Figure 42 yes Figure 41 A sectional view.

[0057] Figure 43 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 3.

[0058] Figure 44 yes Figure 43 A sectional view.

[0059] Figure 45 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 3.

[0060] Figure 46 yes Figure 45 A sectional view.

[0061] Figure 47 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 3.

[0062] Figure 48 yes Figure 47 A sectional view.

[0063] Figure 49 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 4.

[0064] Figure 50 yes Figure 49 A-A' sectional view.

[0065] Figure 51 yes Figure 49 The B-B' sectional view.

[0066] Figure 52 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 4.

[0067] Figure 53 yes Figure 52A-A' sectional view.

[0068] Figure 54 yes Figure 52 The B-B' sectional view.

[0069] Figure 55 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 4.

[0070] Figure 56 yes Figure 55 A-A' sectional view.

[0071] Figure 57 yes Figure 55 The B-B' sectional view.

[0072] Figure 58 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 4.

[0073] Figure 59 yes Figure 58 A-A' sectional view.

[0074] Figure 60 yes Figure 58 The B-B' sectional view.

[0075] Figure 61 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 4.

[0076] Figure 62 yes Figure 61 A-A' sectional view.

[0077] Figure 63 yes Figure 61 The B-B' sectional view.

[0078] Figure 64 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 4.

[0079] Figure 65 yes Figure 64 A-A' sectional view.

[0080] Figure 66 yes Figure 64 The B-B' sectional view.

[0081] Figure 67 yes Figure 64 The C-C' sectional view.

[0082] Figure 68 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 5.

[0083] Figure 69 yes Figure 68 A-A' sectional view.

[0084] Figure 70 yes Figure 68 The B-B' sectional view.

[0085] Figure 71 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 5.

[0086] Figure 72 yes Figure 71 A-A' sectional view.

[0087] Figure 73 yes Figure 71 The B-B' sectional view.

[0088] Figure 74 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 5.

[0089] Figure 75 yes Figure 74 A-A' sectional view.

[0090] Figure 76 yes Figure 74 The B-B' sectional view.

[0091] Figure 77 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 5.

[0092] Figure 78 yes Figure 77 A-A' sectional view.

[0093] Figure 79 yes Figure 77 The B-B' sectional view.

[0094] Figure 80 This is a top view illustrating the manufacturing method of the multi-wavelength integrated semiconductor laser in Embodiment 5.

[0095] Figure 81 yes Figure 80 A-A' sectional view.

[0096] Figure 82 yes Figure 80 The B-B' sectional view. Detailed Implementation

[0097] Embodiments of this disclosure will be described with reference to the accompanying drawings. The same or corresponding components are labeled with the same reference numerals, and sometimes repeated descriptions are omitted.

[0098] Implementation Method 1

[0099] Here, use Figures 1 to 34 This paper describes a method for manufacturing a multi-wavelength integrated semiconductor laser 100, which includes a first semiconductor laser section 110 and a second semiconductor laser section 120 having different oscillation bands.

[0100] First, such as Figure 1 , 2 As shown, a semiconductor layer 2 is epitaxially grown on a semiconductor substrate 1, and an insulating film 3 is formed on the upper surface of the semiconductor layer 2 by a plasma CVD method or the like. Here, the semiconductor layer 2 is a conductive layer such as a p-type or n-type InP layer, or an undoped layer. Examples of materials for the insulating film 3 include SiO2 or SiN.

[0101] Next, as Figure 3 , 4 As shown, the region where the insulating film 3 forms the first semiconductor laser section 110 and the second semiconductor laser section 120 is removed, exposing the semiconductor layer 2. Examples of processing methods for the insulating film 3 include dry etching such as reactive ion etching or inductively coupled plasma etching.

[0102] Then, as Figure 5 , 6 As shown, the semiconductor layer 2 is etched to form two trenches with the semiconductor substrate 1 as the bottom surface and the semiconductor layer 2 as the side surface. Hereinafter, the trench that forms the first semiconductor laser section 110 will be referred to as the first trench 111, and the trench that forms the second semiconductor laser section 120 will be referred to as the second trench 121.

[0103] Although the description is omitted, if necessary, the slots for the third, fourth, ..., nth semiconductor laser sections can also be formed simultaneously.

[0104] Then, the insulating film 3-1 is reformed, as follows: Figure 7 , 8 As shown, the insulating film 3-1 inside the first trench 111 is removed. On the other hand, the inner side of the second trench 121 and the upper surface of the semiconductor layer 2 are masked with the insulating film 3-1 (the first insulating film).

[0105] Furthermore, such as Figure 9 , 10 As shown, the first conductivity layer 4, the first active layer 5, the second conductivity layer 6, the undoped layer 7, and the capping layer 8, which are the semiconductor layers of the first semiconductor laser unit 110, are epitaxially grown sequentially within the first trench 111. Since the insulating film 3-1 acts as a mask, the semiconductor layers of the first semiconductor laser unit 110 are not epitaxially grown on the insulating film 3-1, but are selectively epitaxially grown only within the first trench 111.

[0106] Here, the first conductivity layer 4, the second conductivity layer 6, and the capping layer 8 are layers doped with p-type or n-type InP or other conductivity types. The first active layer 5 and the undoped layer 7 are active layers composed of ternary or quaternary compound semiconductors such as InGaAsP, AlGaInAs, or InGaAs. Furthermore, this is not limited to the first semiconductor laser section 110, but is also common in semiconductor laser sections responsible for oscillations in other wavelength bands.

[0107] Examples of epitaxial growth methods include metal-organic vapor deposition (MOCVD), molecular beam epitaxy (MBE), and liquid phase epitaxy (LPE), but other methods can also be used.

[0108] On the upper surface of the capping layer 8, a protruding crystal growth anomaly 9 is deposited along the edge of the first trench 111 adjacent to the semiconductor layer 2. This crystal growth anomaly 9 is formed by the diffusion and deposition of atoms deposited on the insulating film 3-1 during the epitaxial growth of the semiconductor layer of the first semiconductor laser section 110. The size of the crystal growth anomaly 9 is several μm.

[0109] Next, all of the insulating film 3-1 is removed, and the insulating film 3-2 is reformed. At this point, the abnormal crystal growth region 9 is also covered by the insulating film 3-2. Furthermore, as... Figure 11 , 12 As shown, the insulating film 3-2 inside the second groove 121 is removed. On the other hand, the upper surface of the first semiconductor laser section 110 and the upper surface of the semiconductor layer 2 are masked with the insulating film 3-2 (second insulating film).

[0110] Furthermore, such as Figure 13 , 14 As shown, the first conductivity layer 10, the second active layer 11, the second conductivity layer 12, the undoped layer 13, and the capping layer 14, which are the semiconductor layers of the second semiconductor laser section 120, are epitaxially grown sequentially in the second trench 121. At this time, similar to the case of the first semiconductor laser section 110, a crystal growth anomalous section 15 is deposited on the upper surface of the capping layer 14 along the edge of the second trench 121 adjacent to the semiconductor layer 2.

[0111] In addition, although the explanation is omitted, if necessary, semiconductor layers can also be epitaxially grown inside and outside the trench for the third, fourth... and nth semiconductor laser sections.

[0112] Next, the abnormal crystal growth portions 9 and 15 are removed. Here, the insulating film 3-2 is first removed, and an insulating film 3-3 (the fourth insulating film) is re-formed on the semiconductor layer 2 and the semiconductor layers of the first and second semiconductor laser portions 110 and 120. Furthermore, as... Figure 15 , 16As shown, at the ends of the first and second semiconductor laser sections 110 and 120 adjacent to the semiconductor layer 2, openings are formed in the insulating film 3-3, thereby exposing the crystal growth abnormalities 9 and 15. On the other hand, the upper surfaces of the semiconductor layers of the first and second semiconductor laser sections 110 and 120 without crystal growth abnormalities 9 and 15, and the upper surface of the semiconductor layer 2, are masked by the insulating film 3-3. Furthermore, by performing wet etching, such as... Figure 17 , 18 As shown, abnormal crystal growth regions 9 and 15 are selectively removed.

[0113] It can be assumed that the composition of the crystal growth abnormalities 9 and 15 is the same as the composition of the semiconductor layers of the first and second semiconductor laser sections 110 and 120. Therefore, a solution for etching the semiconductor layers of the first and second semiconductor laser sections 110 and 120 is used in wet etching. Furthermore, it is preferable that the etching rate of the solution relative to the depth direction is slower than the etching rate relative to the lateral direction. Acetic acid is an example of such a solution.

[0114] As described above, the crystal growth anomalies 9 and 15 are several μm in size. If they are not removed, it is impossible to uniformly coat the photoresist 16 in a thickness of several hundred nm in the next process. Therefore, it is necessary to remove the crystal growth anomalies 9 and 15 before coating the photoresist 16.

[0115] In the removal of the abnormal crystal growth parts 9 and 15, wet etching is used instead of dry etching, so it is not necessary to mask them with insulating film 3-3, and a photoresist can also be used for masking.

[0116] In addition, during the etching of the crystal growth abnormality sections 9 and 15, it is sufficient that at least the area on the upper surface of the semiconductor layer of the first and second semiconductor laser sections 110 and 120 that eventually becomes a mesa structure is masked by the insulating film 3-3.

[0117] Next, remove all the insulating film 3-3. Then, as... Figure 19 , 20 As shown, the insulating film 3-4 is reformed again, and photoresist 16 for EB (Electron Beam) exposure is coated on the insulating film 3-4.

[0118] Next, the photoresist 16 is subjected to EB exposure. In the regions where the photoresist 16 forms the first and second semiconductor laser sections 110 and 120, openings are formed at regular intervals along the resonator direction of the laser, exposing the insulating film 3-4. Furthermore, as... Figure 21 , 22 As shown, the exposed insulating film 3-4 is removed, exposing the cover layer 8 and cover layer 14 respectively.

[0119] Furthermore, by performing wet etching or similar methods, the capping layer 8 and undoped layer 7 of the first semiconductor laser section 110 are excavated through the openings in the photoresist 16, exposing the second conductivity layer 6. Simultaneously, for the second semiconductor laser section 120, the capping layer 14 and undoped layer 13 are also excavated, exposing the second conductivity layer 12. Then, by removing the photoresist 16, a... Figure 23 , 24 The state.

[0120] Then, as Figure 25 , 26 As shown, remove the insulating film 3-4 from the upper surface. Then, as... Figure 27 , 28 As shown, by epitaxially growing a buried layer 17 on the portion of the undoped layer 7 and capping layer 8 that is excavated in the first semiconductor laser section 110, a diffraction grating is formed, which consists of a grating of undoped layer 7 and capping layer 8 arranged at certain intervals along the resonator direction of the laser. Similarly, for the second semiconductor laser section 120, a diffraction grating is formed by burying the capping layer 14 and undoped layer 13 with the buried layer 17.

[0121] As the buried layer 17, a ternary or quaternary mixed-crystal semiconductor such as InGaAsP, AlGaInAs, or InGaAs is used.

[0122] Next, after epitaxially growing the contact layer 19 on the landfill layer 17, an insulating film 3-5 is formed. Furthermore, as... Figure 29 , 30 As shown, the areas of the first semiconductor laser unit 110 and the second semiconductor laser unit 120 that have a mesa structure are masked by an insulating film 3-5 (third insulating film), and the insulating film 3-5 in other areas is removed.

[0123] Then, as Figure 31 , 32 As shown, the contact layer 19, the buried layer 17, the semiconductor layer 2, and the first conductive layer 4, the first active layer 5, the second conductive layer 6, the undoped layer 7 (not shown), and the capping layer 8 (not shown) of the first semiconductor laser section 110, as well as the first conductive layer 10, the second active layer 11, the second conductive layer 12, the undoped layer 13 (not shown), and the capping layer 14 (not shown) of the second semiconductor laser section 120 are removed by dry etching, exposing the semiconductor substrate 1. In this way, the first and second semiconductor laser sections 110 and 120 are simultaneously dry-etched, thereby forming a mesa structure together.

[0124] Next, remove all the insulating film 3-5. Then, as... Figure 33 , 34As shown, an insulating film 3 is formed on the sidewalls of the mesa structures of the first and second semiconductor laser sections 110 and 120, as well as on the semiconductor substrate 1, and an electrode 20 is formed on the upper part of each mesa structure. In addition, an electrode 20 is also formed on the back side of the semiconductor substrate 1. As a result, a multi-wavelength integrated semiconductor laser 100 having a mesa-type first semiconductor laser section 110 and a second semiconductor laser section 120 can be manufactured.

[0125] As described above, in this disclosure, the semiconductor layer 2 formed on the semiconductor substrate 1 is etched, simultaneously forming a first trench 111 and a second trench 121. A semiconductor layer of the first semiconductor laser portion 110 is selectively epitaxially grown inside the first trench 111, and a semiconductor layer of the second semiconductor laser portion 120 is selectively epitaxially grown inside the second trench 121. Since the semiconductor layers of the first and second semiconductor laser portions 110 and 120 can be epitaxially grown on the semiconductor substrate 1 from the surfaces on which the same etching has been performed, the heights of the first active layer 5 and the second active layer 11 can be made identical.

[0126] <Variation Example 1>

[0127] The above describes the formation of a first conductivity layer 4, a first active layer 5, a second conductivity layer 6, an undoped layer 7, and a capping layer 8 within the first trench 111 of the first semiconductor laser section 110. However, it is sufficient that at least the first active layer 5 is formed within the first trench 111. For example, the first conductivity layer 4 can be formed outside the first trench 111, identical to the semiconductor substrate 1. Alternatively, the second conductivity layer 6 can also be formed on top of the first trench 111. Furthermore, the undoped layer 7 and the capping layer 8 are not necessarily required. Similarly, it is sufficient that at least the second active layer 11 is formed within the second trench 121. This principle is consistent throughout all the embodiments described below.

[0128] Implementation Method 2

[0129] In this embodiment, a method for manufacturing a buried ridge type multi-wavelength integrated semiconductor laser 100 is shown. Furthermore, in Embodiment 1... Figures 1 to 32 The explanation is also common in this embodiment, so it is omitted here.

[0130] exist Figure 32 After the processes up to this point, such as Figure 35 , 36 As shown, a current blocking layer 18 is epitaxially grown in a mesa structure that buries the first and second semiconductor laser sections 110 and 120. Furthermore, the material of the current blocking layer 18 can be, for example, a structure in which p-type InP and n-type InP are alternately stacked, or a semi-insulator such as Fe-doped InP, but the type is not limited as long as it is a material with high resistance to the current flowing in the first active layer 5 and the second active layer 11.

[0131] On the upper surface of the current blocking layer 18, crystal growth aberrations (not shown) are sometimes deposited along the edge of the mesa structure. Similar to Embodiment 1, these crystal growth aberrations are formed by atomic diffusion and deposition of the insulating film 3 during the epitaxial growth of the current blocking layer 18. The deposited crystal growth aberrations are masked using the same method as in Embodiment 1 and then removed by wet etching.

[0132] Then, remove the insulating film 3 from the upper part of the countertop structure. Then, as... Figure 37 , 38 As shown, a contact layer 19 is epitaxially grown on top of the current blocking layer 18. The contact layer 19 can be a ternary or quaternary mixed-crystal semiconductor such as InGaAsP, AlGaInAs, or InGaAs.

[0133] Furthermore, an insulating film 3 is reformed on the contact layer 19, such as... Figure 39 , 40 As shown, the insulating film 3 on the upper part of the mesa structure of the first and second semiconductor laser sections 110 and 120 is removed to expose the contact layer 19.

[0134] Then, as Figure 41 , 42 As shown, an electrode 20 is formed on the upper part of the exposed contact layer 19, and an electrode 20 is also formed on the back side of the semiconductor substrate 1. This allows for the fabrication of a buried ridge type multi-wavelength integrated semiconductor laser 100 where each mesa structure is filled with a current blocking layer 18. The current blocking layer 18 restricts the amount of current flowing between the electrodes 20 formed on the upper part of the contact layer 19 and the back side of the semiconductor substrate 1. This suppresses heat generation during laser operation. In terms of stable operation, the multi-wavelength integrated semiconductor laser 100 of this embodiment exhibits superior performance compared to the multi-wavelength integrated semiconductor laser 100 of Embodiment 1.

[0135] Implementation Method 3

[0136] In this embodiment, a method for manufacturing a multi-wavelength integrated semiconductor laser 100 that can achieve a higher degree of uniformity in the height of the first active layer 5 of the first semiconductor laser section 110 and the second active layer 11 of the second semiconductor laser section 120 compared to Embodiment 1 will be described. Furthermore, the changes from Embodiment 1 will be explained below.

[0137] First, such as Figure 43 , 44As shown, an etch stop layer 30 and a semiconductor layer 2 are epitaxially grown sequentially on a semiconductor substrate 1, and an insulating film 3 is formed on the upper surface of the semiconductor layer 2. The etch stop layer 30 is a semiconductor layer that prevents etching of the semiconductor substrate 1, and is made of a material capable of selectively etching the semiconductor substrate 1. For example, if the semiconductor substrate 1 is InP, the etch stop layer 30 can be a ternary or quaternary mixed-crystal semiconductor such as InGaAsP, AlGaInAs, or InGaAs.

[0138] Next, as Figure 45 , 46 As shown, the region of the insulating film 3 forming the first semiconductor laser section 110 and the second semiconductor laser section 120 is removed, exposing the semiconductor layer 2.

[0139] Then, the semiconductor layer 2 is wet-etched using the first chemical solution to form the first trench 111 and the second trench 121, exposing the etch stop layer 30 on the bottom surface of the two trenches. Furthermore, as... Figure 47 , 48 As shown, the exposed etch stop layer 30 is wet-etched using the second chemical solution to expose the semiconductor substrate 1. Subsequent processes are the same as in Embodiment 1. Figure 7 The same applies thereafter, therefore the explanation is omitted.

[0140] Here, the first etching solution is one that has an etching rate for the semiconductor layer 2, and hydrochloric acid is commonly used. If the first etching solution also has an etching rate for the etch stop layer 30, etching can be performed simultaneously from the semiconductor layer 2 to the etch stop layer 30. However, as described in Embodiment 1, the semiconductor layer 2 is mostly made of InP. Hydrochloric acid has an etching rate for InP, but not for InGaAsP, AlGaInAs, or InGaAs; therefore, etching of the etch stop layer 30 is not performed.

[0141] The second etching solution is a solution that enables selective etching between the etch stop layer 30 and the semiconductor substrate 1. That is, it is a solution with a higher etching rate for the etch stop layer 30 than for the semiconductor substrate 1, such as tartaric acid.

[0142] In this way, by forming an etch stop layer 30 between the semiconductor substrate 1 and the semiconductor layer 2, which enables selective etching of the semiconductor substrate 1, over-etching of the semiconductor substrate 1 can be prevented. The height of the surface on the semiconductor substrate 1 at which the epitaxial growth of the semiconductor layers of the first and second semiconductor laser sections 110 and 120 begins can be precisely controlled, so the heights of the first active layer 5 of the first semiconductor laser section 110 and the second active layer 11 of the second semiconductor laser section 120 can be more precisely matched than in Embodiment 1.

[0143] <Variation Example 2>

[0144] Furthermore, the etching of the semiconductor layer 2 and the etch stop layer 30 does not necessarily have to be wet etching; it can also be dry etching. By observing the plasma emission of the elements contained in the etch stop layer 30 and using it for endpoint detection, over-etching of the semiconductor substrate 1 can be prevented even in dry etching. Thus, the same effect as in Embodiment 3 can be obtained.

[0145] Implementation Method 4

[0146] In this embodiment, a method for manufacturing a multi-wavelength integrated semiconductor laser 100 with a built-in modulator or optical amplifier is shown. Furthermore, the following description will explain a method for manufacturing the multi-wavelength integrated semiconductor laser 100 with a built-in modulator. Regarding the optical amplifier, in the following description, the modulator will be replaced with an optical amplifier.

[0147] Furthermore, in the accompanying drawings of this embodiment, the cross section labeled A-A' represents the cross section of the region where the first and second semiconductor laser units 110 and 120 are located. The cross section labeled B-B' represents the cross section of the region where the first and second modulators 130 and 140 are located. The cross section labeled C-C' represents the cross section of the region where the first semiconductor laser unit 110 and the first modulator 130 are located.

[0148] First, a first cladding layer 21, a core layer 22, and a second cladding layer 23, serving as waveguide layers, are sequentially epitaxially grown on a semiconductor substrate 1, forming the semiconductor layer 2. Next, an insulating film 3 is formed on the upper surface of the second cladding layer 23. Then, as... Figures 49-51 As shown, the region of the insulating film 3 forming the first and second semiconductor laser sections 110, 120 and the first and second modulators 130, 140 is removed to expose the second cladding layer 23.

[0149] Here, the first cladding layer 21 and the second cladding layer 23 are undoped InP or the like. In addition, the core layer 22 is an undoped ternary or quaternary mixed-crystal semiconductor such as InGaAsP, AlGaInAs, or InGaAs.

[0150] Then, as Figures 52-54 As shown, the second cladding layer 23, the core layer 22, and the first cladding layer 21 are etched, exposing the semiconductor substrate 1 except for the portion masked by the insulating film 3. This forms four trenches in the semiconductor layer 2 composed of the first cladding layer 21, the core layer 22, and the second cladding layer 23. Hereinafter, the four trenches will be designated as the first trench 111, the second trench 121, the third trench 131, and the fourth trench 141.

[0151] Next, after masking the inner sides of the third and fourth grooves 131 and 141 and the upper surface of the second covering layer 23 with insulating film 3, the following method is used: Figures 7-28The method shown manufactures the first and second semiconductor laser sections 110 and 120. Thus, as Figures 55-57 As shown, semiconductor layers are formed for the first and second semiconductor laser sections 110 and 120, respectively. On the other hand, the inner sides of the third and fourth trenches 131 and 141 and the upper surface of the second cladding layer 23 separated by these trenches are covered by an insulating film 3.

[0152] Furthermore, using the same method as in Implementation Method 1, such as... Figures 58-60 As shown, the first conductivity layer 24, the third active layer 25, and the second conductivity layer 26, which serve as the semiconductor layer of the first modulator 130, are selectively epitaxially grown sequentially in the third trench 131. Furthermore, the first conductivity layer 27, the fourth active layer 28, and the second conductivity layer 29, which serve as the semiconductor layer of the second modulator 140, are selectively epitaxially grown sequentially in the fourth trench 141.

[0153] Here, the first conductivity layers 24 and 27 and the second conductivity layers 26 and 29 are InP or the like, doped with p-type or n-type. Furthermore, the third active layer 25 and the fourth active layer 28 are active layers composed of ternary or quaternary mixed-crystal semiconductors such as InGaAsP, AlGaInAs, or InGaAs.

[0154] Furthermore, the crystal growth abnormalities deposited on the upper surface of the semiconductor layers of the first and second modulators 130 and 140 are removed by the method shown in Embodiment 1.

[0155] Next, after epitaxially growing contact layers 19 on the upper surfaces of the semiconductor layers of the first and second semiconductor laser units 110 and 120 and the semiconductor layers of the first and second modulators 130 and 140, an insulating film 3 is formed. Then, the regions forming the mesa structures of the first and second semiconductor laser units 110 and 120 and the first and second modulators 130 and 140 are retained, and the insulating film 3 is removed, as shown below. Figures 61-63 As shown, this exposes the contact layer 19.

[0156] Next, the semiconductor layers of the contact layer 19, the first and second semiconductor laser sections 110 and 120, and the first and second modulators 130 and 140 are removed by dry etching, exposing the semiconductor substrate 1 except for the portions masked by the insulating film 3. Thus, as... Figures 64-67 As shown, a mesa structure is formed together with the first and second semiconductor laser sections 110 and 120 and the first and second modulators 130 and 140.

[0157] like Figure 67As shown, the first active layer 5 of the first semiconductor laser unit 110 is connected to the third active layer 25 of the first modulator 130 via the core layer 22. In this disclosure, the first active layer 5 and the third active layer 25 can be made to have the same height, thus enabling the light oscillating from the first semiconductor laser unit 110 to be waveguided to the first modulator 130 without loss. The same applies to the relationship between the second semiconductor laser unit 120 and the second modulator 140.

[0158] Furthermore, in this disclosure, such as Figure 67 As shown, the thickness of the core layer 22 in a side view is greater than the thickness of the first active layer 5 of the first semiconductor laser unit 110 and the third active layer 25 of the first modulator 130. Therefore, even if the heights of the first active layer 5 and the third active layer 25 are unintentionally offset, the effect of the offset can be mitigated. The same applies to the relationship between the second semiconductor laser unit 120 and the second modulator 140.

[0159] Although the accompanying drawings are omitted below, as described in Embodiment 1, an insulating film 3 is formed on the sidewalls of the mesa structures of the first and second semiconductor laser sections 110 and 120, the sidewalls of the mesa structures of the first and second modulators 130 and 140, the sidewalls of the mesa structure of the semiconductor layer 2, and the semiconductor substrate 1. Furthermore, electrodes 20 are formed on the upper part of these mesa structures. Additionally, electrodes 20 are also formed on the back side of the semiconductor substrate 1. Thus, a multi-wavelength integrated semiconductor laser 100 with a built-in modulator can be manufactured.

[0160] Implementation Method 5

[0161] This embodiment illustrates a method for manufacturing a multi-wavelength integrated semiconductor laser 100 with an integrated optical coupler. In the accompanying drawings of this embodiment, the section labeled A-A' represents a cross-section of the region where the first and second semiconductor laser sections 110 and 120 are located. Furthermore, the section labeled B-B' represents a cross-section of the region where the optical coupler 150 is located.

[0162] First, a first cladding layer 21, a core layer 22, and a second cladding layer 23, serving as waveguide layers, are sequentially epitaxially grown on a semiconductor substrate 1, forming the semiconductor layer 2. Then, an insulating film 3 is formed on the upper surface of the second cladding layer 23. Next, as... Figures 68-70 As shown, the regions where the insulating film 3 forms the first and second semiconductor laser sections 110 and 120 are removed, exposing the second cladding layer 23. On the other hand, the regions where the second cladding layer 23 forms the optical coupler 150 are masked by the insulating film 3.

[0163] Then, as Figures 71-73As shown, the second cladding layer 23, the core layer 22, and the first cladding layer 21 are etched to expose the semiconductor substrate 1, except for the portion covered by the insulating film 3. This forms the first trench 111 and the second trench 121.

[0164] Next, through implementation method 1 Figures 7-28 The method shown manufactures the first and second semiconductor laser sections 110 and 120. Thus, as... Figures 74-76 As shown, the semiconductor layers forming the first and second semiconductor laser sections 110 and 120 have a contact layer 19 formed on their upper surfaces. On the other hand, in the region where the optical coupler 150 is formed, the upper surface of the second cladding layer 23 is masked by an insulating film 3.

[0165] Next, the insulating film 3 is completely removed, and a new insulating film 3 is formed. Then, as... Figures 77-79 As shown, the regions that form the mesa structures of the first and second semiconductor laser sections 110 and 120, and the region that forms the optical coupler 150, are retained, and the insulating film 3 is removed. As a result, in the regions where the first and second semiconductor laser sections 110 and 120 are formed, the contact layer 19 is exposed except for the portion covered by the insulating film 3, and in the region where the optical coupler 150 is formed, the second covering layer 23 is exposed except for the portion covered by the insulating film 3.

[0166] Next, as Figures 80-82 As shown, the contact layer 19, the semiconductor layers of the first and second semiconductor laser sections 110 and 120, and the semiconductor layer of the optocoupler 150 are removed by dry etching, exposing the semiconductor substrate 1 except for the portion masked by the insulating film 3. Thus, the mesa structure of the first and second semiconductor laser sections 110 and 120 and the optocoupler 150 are formed together. When the optocoupler 150 is a multimode interference waveguide, it includes a multiplexer, an input device branching from the multiplexer and connected to the first active layer 5 of the first semiconductor laser section 110 and the second active layer 11 of the second semiconductor laser section 120, and an output device extending from the multiplexer. However, the shape of the optocoupler 150 is not limited to this.

[0167] In this disclosure, the first active layer 5 of the first semiconductor laser unit 110, the second active layer 11 of the second semiconductor laser unit 120, and the core layer 22 of the optical coupler 150 can be made to have the same height, so that the light oscillating from the semiconductor laser unit can be waveguided to the optical coupler 150 without loss.

[0168] Although the accompanying drawings are omitted below, as described in Embodiment 1, an insulating film 3 is formed on the sidewalls of the mesa structures of the first and second semiconductor laser units 110 and 120, the sidewalls of the optocoupler 150, and the semiconductor substrate 1. Furthermore, an electrode 20 is formed on the upper part of the mesa structures of the first and second semiconductor laser units 110 and 120. Additionally, an electrode 20 is also formed on the back side of the semiconductor substrate 1. Thus, a multi-wavelength integrated semiconductor laser 100 with a built-in optocoupler 150 can be manufactured.

[0169] As described above, according to this disclosure, a method for manufacturing a multi-wavelength integrated semiconductor laser can be provided that enables the active layers of multiple semiconductor laser sections, each responsible for laser oscillation in different wavelength bands, to have a high degree of uniformity.

[0170] Furthermore, this disclosure is not limited to the above-described embodiments, and various modifications can be made during implementation without departing from its spirit. Additionally, the various embodiments and modifications can be appropriately combined to achieve combined effects.

[0171] Explanation of reference numerals in the attached figures

[0172] 1…Semiconductor substrate; 2…Semiconductor layer; 3…Insulating film; 4…First conductivity layer; 5…First active layer; 6…Second conductivity layer; 7…Undoped layer; 8…Capping layer; 9…Crystal growth anomaly; 10…First conductivity layer; 11…Second active layer; 12…Second conductivity layer; 13…Undoped layer; 14…Capping layer; 15…Crystal growth anomaly; 16…Photoresist; 17…Buried layer; 18…Current blocking layer; 19…Contact layer; 20…Electrode; 21…First cladding layer; 22…Core layer; 23…Second cladding layer; 24…First conductive layer; 25…Third active layer; 26…Second conductive layer; 27…First conductive layer; 28…Fourth active layer; 29…Second conductive layer; 30…Etch stop layer; 100…Multi-wavelength integrated semiconductor laser; 110…First semiconductor laser section; 111…First slot; 120…Second semiconductor laser section; 121…Second slot; 130…First modulator; 131…Third slot; 140…Second modulator; 141…Fourth slot; 150…Optical coupler.

Claims

1. A method for manufacturing a multi-wavelength integrated semiconductor laser, characterized in that, The process includes the following steps: The process of epitaxially growing a semiconductor layer on a semiconductor substrate; The process of etching the semiconductor layer to simultaneously form the first trench and the second trench; The process of forming a first semiconductor laser part by epitaxially growing at least a first active layer in the first trench, based on masking the inner side of the second trench and the upper surface of the semiconductor layer with a first insulating film; After removing the first insulating film, and masking the upper surface of the first semiconductor laser portion and the upper surface of the semiconductor layer with a second insulating film, a second active layer is epitaxially grown in the second trench to form a second semiconductor laser portion; and After removing the second insulating film, and masking a portion of the upper surface of the first semiconductor laser portion and the upper surface of the second semiconductor laser portion with a third insulating film, dry etching is performed on the first semiconductor laser portion, the second semiconductor laser portion, and the semiconductor layer to form the mesa structure of the first semiconductor laser portion and the mesa structure of the second semiconductor laser portion.

2. The method for manufacturing a multi-wavelength integrated semiconductor laser according to claim 1, characterized in that, It also includes the following processes: Before forming the third insulating film, a fourth insulating film or photoresist is formed on the semiconductor layer, the first semiconductor laser portion, and the second semiconductor laser portion, and an opening is formed in the fourth insulating film or the photoresist at the ends of the first semiconductor laser portion and the second semiconductor laser portion adjacent to the semiconductor layer. and A process of selectively removing crystal growth abnormalities deposited on the ends of the first semiconductor laser section and the second semiconductor laser section by using wet etching with the fourth insulating film or the resist having the opening formed thereon as a mask.

3. The method for manufacturing a multi-wavelength integrated semiconductor laser according to claim 2, characterized in that, In the wet etching, a solution with a slower etching rate in the depth direction than in the lateral direction is used.

4. The method for manufacturing a multi-wavelength integrated semiconductor laser according to claim 2 or 3, characterized in that, The upper surface of the first active layer in the first trench and the upper surface of the second active layer in the second trench include an undoped layer. The manufacturing method of the multi-wavelength integrated semiconductor laser further includes the following steps: after removing the abnormal crystal growth portion, forming a diffraction grating in which gratings including the undoped layer are arranged in the resonator direction of the first semiconductor laser portion and the second semiconductor laser portion.

5. The method for manufacturing a multi-wavelength integrated semiconductor laser according to any one of claims 1 to 4, characterized in that, It also includes the following processes: An etch stop layer is formed on the semiconductor substrate, and the semiconductor layer is formed on the etch stop layer. After the first trench and the second trench are formed in the semiconductor layer, the etch stop layer exposed on the bottom surface of the first trench and the second trench is selectively etched relative to the semiconductor substrate.

6. The method for manufacturing a multi-wavelength integrated semiconductor laser according to claim 5, characterized in that, When etching the etch stop layer, wet etching is performed using a solution with a higher etch rate on the etch stop layer than on the semiconductor substrate.

7. The method for manufacturing a multi-wavelength integrated semiconductor laser according to claim 5, characterized in that, During dry etching of the etch stop layer, the endpoint of the etching is detected by observing the plasma luminescence of the etch stop layer.

8. The method for manufacturing a multi-wavelength integrated semiconductor laser according to any one of claims 1 to 7, characterized in that, The process includes the step of filling the mesa structure of the first semiconductor laser part and the second semiconductor laser part with a current blocking layer.

9. A method for manufacturing a multi-wavelength integrated semiconductor laser according to any one of claims 1 to 8, characterized in that, It also includes the step of forming a third trench in the semiconductor layer simultaneously with the first trench and the second trench, and forming a modulator or optical amplifier in the third trench.

10. The method for manufacturing a multi-wavelength integrated semiconductor laser according to claim 9, characterized in that, The semiconductor layer is a waveguide layer that includes a core layer. The thickness of the core layer when viewed from the side is greater than the thickness of the first active layer and the second active layer, as well as the thickness of the active layer of the modulator or the optical amplifier.

11. A method for manufacturing a multi-wavelength integrated semiconductor laser according to any one of claims 1 to 8, characterized in that, It also includes the step of forming an optical coupler on the semiconductor layer. The semiconductor layer has a waveguide layer. The first active layer and the second active layer are connected to the optical coupler via the waveguide layer.

Images