Semiconductor laser with power monitoring function

Abstract

The invention relates to a semiconductor laser with power monitoring, which comprises a lower electrode layer, a substrate layer, a lower cover layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a laser ridge layer, a detector coupling layer and an insulating filling layer, and is characterized in that the lower electrode layer, the substrate layer, the lower cover layer, the lower waveguide layer, the multi-quantum well layer and the upper waveguide layer are sequentially stacked from bottom to top; the laser ridge layer, the detector coupling layer and the insulating filling layer are located on the upper waveguide layer, the detector coupling layer and the laser ridge layer are arranged at intervals, and the insulating filling layer wraps local parts of the laser ridge layer and the detector coupling layer; the first upper electrode layer at the upper end of the laser ridge layer and the second upper electrode layer at the upper end of the detector coupling layer are exposed, the detector coupling layer is electrically isolated from the laser ridge layer, and optical coupling is established. According to the semiconductor laser, the laser ridge layer and the detector coupling layer are prepared on the upper waveguide layer at the same time, and power monitoring can be achieved while the manufacturing and packaging cost is not increased.

Description

Technical Field

[0001] The invention relates to the technical field of photon optoelectronic device design, and in particular to a semiconductor laser with built-in power monitoring. Background Art

[0002] Semiconductor lasers have a wide range of uses. They can be used in spectroscopy, photochemistry, medicine, biology, integrated optics, pollution monitoring, semiconductor material processing, optical device characteristic evaluation, optical integrated circuit testing, quantum optical information processing and communications. Therefore, it can be seen that semiconductor lasers have important applications in many fields. However, during the application process, external detectors are usually required to monitor the working status of the semiconductor laser, which increases the packaging cost. Summary of the invention

[0003] The purpose of the present invention is to provide a semiconductor laser with built-in power monitoring, so that the laser and the detector can be prepared simultaneously during the manufacturing process, solving the problem of power monitoring in the later stage and reducing the packaging cost.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A semiconductor laser with built-in power monitoring comprises a lower electrode layer, a substrate layer, a lower cover layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a laser ridge stripe layer, a detector coupling layer and an insulating filling layer, wherein the lower electrode layer, the substrate layer, the lower cover layer, the lower waveguide layer, the multi-quantum well layer and the upper waveguide layer are sequentially stacked from bottom to top, the laser ridge stripe layer, the detector coupling layer and the insulating filling layer are all arranged on the upper waveguide layer, the detector coupling layer and the laser ridge stripe layer are arranged at intervals, the insulating filling layer wraps the laser ridge stripe layer and a part of the detector coupling layer therein, so that a first upper electrode layer at the upper end of the laser ridge stripe layer and a second upper electrode layer at the upper end of the detector coupling layer are exposed, the detector coupling layer is electrically isolated from the laser ridge stripe layer, and optical coupling is established.

[0006] In one embodiment of the present application, the laser ridge layer includes a ridge lower layer, a ridge middle layer and a ridge upper layer stacked in sequence from bottom to top, the ridge lower layer is an InP ridge lower layer or an InAlGaAs ridge lower layer that has undergone P-type modulation doping, the ridge middle layer is an InGaAs ridge middle layer that has undergone P-type modulation doping, the ridge upper layer is the first upper electrode layer, and the ridge upper layer includes a first titanium layer and a first gold layer that are stacked in sequence from bottom to top.

[0007] In one embodiment of the present application, a size of the laser ridge layer along a first direction perpendicular to the stacking direction is 150 μm to 4000 μm, a size of the laser ridge layer along a second direction perpendicular to the stacking direction is 2 μm to 100 μm, the first direction is perpendicular to the second direction, and the size of the laser ridge layer along the stacking direction is 0.9 μm to 1.2 μm.

[0008] In one embodiment of the present application, the detector coupling layer includes a curved strip portion and a cylindrical portion, the first end of the curved strip portion is close to the laser ridge layer, the second end of the curved strip portion is bent and extended in a direction away from the laser ridge layer, and the second end of the curved strip portion is connected to the cylindrical portion.

[0009] In one embodiment of the present application, a size of the curved strip-like portion along a first direction perpendicular to the stacking direction is 20 μm to 30 μm, a size of the curved strip-like portion along a second direction perpendicular to the stacking direction is 2 μm to 3 μm, the first direction is perpendicular to the second direction, the size of the curved strip-like portion along the stacking direction is 0.9 μm to 1.2 μm, a diameter of the cylindrical portion is 50 μm to 60 μm, and a size of the cylindrical portion along the stacking direction is 0.9 μm to 1.2 μm.

[0010] In one embodiment of the present application, the detector coupling layer includes a coupling lower layer, a coupling middle layer and a coupling upper layer stacked in sequence from bottom to top, the coupling lower layer is an InP coupling lower layer or an InAlGaAs coupling lower layer that has undergone P-type modulation doping, the coupling middle layer is an InGaAs coupling middle layer that has undergone P-type modulation doping, the coupling upper layer is a second upper electrode layer, and the coupling upper layer includes a second titanium layer and a second gold layer that are stacked in sequence from bottom to top.

[0011] In one embodiment of the present application, the lower electrode layer includes a third gold layer and a third titanium layer stacked in sequence from bottom to top, or the lower electrode layer includes a third gold layer and a gold-germanium-nickel layer stacked in sequence from bottom to top, the size of the third gold layer along the stacking direction is not less than 300nm, and the size of the third titanium layer or the gold-germanium-nickel layer along the stacking direction is not less than 40nm.

[0012] In one embodiment of the present application, the substrate layer is a GaAs substrate layer or an InP substrate layer that has been subjected to N-type modulation doping, and a size of the substrate layer along the stacking direction is 100 μm to 120 μm.

[0013] In one embodiment of the present application, the lower cover layer is an InP lower cover layer or an AlGaAs lower cover layer that has been subjected to N-type modulation doping, and a size of the lower cover layer along the stacking direction is not less than 1.6 μm.

[0014] In one embodiment of the present application, the lower waveguide layer is an InGaAsP waveguide layer or an AlGaInAs waveguide layer, the size of the lower waveguide layer along the stacking direction is not less than 0.5 μm, the refractive index of the lower waveguide layer gradually increases from bottom to top, and the maximum refractive index does not exceed 3.55.

[0015] In one embodiment of the present application, the multi-quantum well layer is an InGaAs multi-quantum well layer or an InGaAsP multi-quantum well layer, the size of the multi-quantum well layer along the stacking direction is 10nm~120nm, the multi-quantum well layer includes 1~9 quantum wells, the well layer thickness is 3nm~9nm, and the barrier layer thickness is 5nm~12nm.

[0016] In one embodiment of the present application, the upper waveguide layer is an InGaAsP waveguide layer or an AlGaInAs waveguide layer, the size of the upper waveguide layer along the stacking direction is not less than 0.9 μm, the refractive index of the upper waveguide layer gradually decreases from bottom to top, and the minimum refractive index is not less than 2.9.

[0017] In one embodiment of the present application, the insulating filling layer is a silicon oxide layer or a silicon nitride layer.

[0018] It can be seen from the above technical scheme that the present invention discloses a semiconductor laser with built-in power monitoring, which includes a lower electrode layer, a substrate layer, a lower cover layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a laser ridge stripe layer, a detector coupling layer and an insulating filling layer, wherein the lower electrode layer, the substrate layer, the lower cover layer, the lower waveguide layer, the multi-quantum well layer and the upper waveguide layer are stacked in sequence from bottom to top, the laser ridge stripe layer, the detector coupling layer and the insulating filling layer are all arranged on the upper waveguide layer, the detector coupling layer and the laser ridge stripe layer are arranged at intervals, the insulating filling layer wraps the laser ridge stripe layer and the detector coupling layer partially, so that the first upper electrode layer at the upper end of the laser ridge stripe layer and the second upper electrode layer at the upper end of the detector coupling layer are exposed, the detector coupling layer is electrically isolated from the laser ridge stripe layer, and optical coupling is established.

[0019] It can be seen that during the preparation process of the above-mentioned semiconductor laser with built-in power monitoring, the laser ridge layer and the detector coupling layer are simultaneously prepared on the upper waveguide layer. Compared with the existing single semiconductor laser, the purpose of power monitoring of the semiconductor laser is achieved without increasing the manufacturing and packaging costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the structure of a semiconductor laser with built-in power monitoring provided by an embodiment of the present invention;

[0022] Figure 2 A top view of a semiconductor laser with built-in power monitoring provided by an embodiment of the present invention.

[0023] In the figure:

[0024] 1 is the lower electrode layer; 2 is the substrate layer; 3 is the lower cover layer; 4 is the lower waveguide layer; 5 is the multi-quantum well layer; 6 is the upper waveguide layer; 7 is the laser ridge layer; 8 is the detector coupling layer; 801 is the curved strip portion; 802 is the cylindrical portion; and 9 is the insulating filling layer. DETAILED DESCRIPTION

[0025] The core of the present invention is to provide a semiconductor laser with built-in power monitoring. The structural design of the semiconductor laser with built-in power monitoring enables the laser and the detector to be prepared simultaneously during the manufacturing process, thereby solving the problem of power monitoring in the later stage and reducing the packaging cost.

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 and Figure 2 , Figure 1 A schematic diagram of the structure of a semiconductor laser with built-in power monitoring provided by an embodiment of the present invention, Figure 2 A top view of a semiconductor laser with built-in power monitoring provided by an embodiment of the present invention.

[0028] A semiconductor laser with built-in power monitoring is disclosed in an embodiment of the present invention. The semiconductor laser with built-in power monitoring includes a lower electrode layer 1, a substrate layer 2, a lower cover layer 3, a lower waveguide layer 4, a multi-quantum well layer 5, an upper waveguide layer 6, a laser ridge layer 7, a detector coupling layer 8 and an insulating filling layer 9.

[0029] Among them, the lower electrode layer 1, the substrate layer 2, the lower cover layer 3, the lower waveguide layer 4, the multi-quantum well layer 5 and the upper waveguide layer 6 are stacked in sequence from bottom to top, the laser ridge layer 7, the detector coupling layer 8 and the insulating filling layer 9 are all arranged on the upper waveguide layer 6, the detector coupling layer 8 and the laser ridge layer 7 are arranged at intervals, the insulating filling layer 9 wraps the laser ridge layer 7 and the detector coupling layer 8 partially, so that the first upper electrode layer at the upper end of the laser ridge layer 7 and the second upper electrode layer at the upper end of the detector coupling layer 8 are exposed, the detector coupling layer 8 is electrically isolated from the laser ridge layer 7, and optical coupling is established, the lower electrode layer 1 serves as the negative electrode of the laser and the positive electrode of the detector at the same time, that is, the laser and the detector share the lower electrode layer 1, the first upper electrode layer serves as the positive electrode of the laser, and the positive voltage end of the laser is loaded thereby, and the second upper electrode layer serves as the negative electrode of the detector, and the negative voltage end of the detector is loaded thereby.

[0030] Compared with the prior art, during the preparation process of the semiconductor laser with built-in power monitoring provided by the embodiment of the present invention, a laser ridge layer 7 and a detector coupling layer 8 are simultaneously prepared on the upper waveguide layer 6, thereby achieving the purpose of power monitoring of the semiconductor laser without increasing the manufacturing and packaging costs.

[0031] In one embodiment of the present application, the laser ridge stripe layer 7 includes a ridge stripe lower layer, a ridge stripe middle layer and a ridge stripe upper layer stacked in sequence from bottom to top, and the ridge stripe lower layer is an InP ridge stripe lower layer or an InAlGaAs ridge stripe lower layer that is P-type modulation doped, and the P-type doping concentration is 4×10 18 cm -3 Up to 9×10 18 cm -3 The ridge stripe middle layer is an InGaAs ridge stripe middle layer with P-type modulation doping. The ridge stripe middle layer serves as a contact layer with a P-type doping concentration of 1×10 19 cm -3 Up to 2×10 19 cm -3 The upper layer of the ridge strip is the first upper electrode layer, which adopts a double-layer structure, including a first titanium layer and a first gold layer stacked from bottom to top. The laser current is injected from the first upper electrode layer.

[0032] Specifically, the size of the laser ridge layer 7 along a first direction perpendicular to the stacking direction is 150μm~4000μm, the size of the laser ridge layer 7 along a second direction perpendicular to the stacking direction is 2μm~100μm, the first direction is perpendicular to the second direction, the size of the laser ridge layer 7 along the stacking direction is 0.9μm~1.2μm, wherein the size of the ridge middle layer along the stacking direction is 0.2μm~0.4μm, the size of the first titanium layer along the stacking direction is 50nm~100nm, and the size of the first gold layer along the stacking direction is not less than 300nm.

[0033] like Figure 1 and Figure 2 As shown, in one embodiment of the present application, the detector coupling layer 8 includes a curved strip portion 801 and a cylindrical portion 802, the first end of the curved strip portion 801 is close to the laser ridge layer 7, and the second end of the curved strip portion 801 is bent and extended in a direction away from the laser ridge layer 7, that is, the second end of the curved strip portion 801 is along the length direction of the laser ridge layer 7, that is, extends in the above-mentioned first direction, and bends in a direction away from the laser ridge layer 7, and the second end of the curved strip portion 801 is connected to the cylindrical portion 802.

[0034] Specifically, the size of the curved strip portion 801 along a first direction perpendicular to the stacking direction is 20μm~30μm, the size of the curved strip portion 801 along a second direction perpendicular to the stacking direction is 2μm~3μm, the minimum distance between the first end of the curved strip portion 801 and the laser ridge layer 7 is 1μm, the first direction is perpendicular to the second direction, the size of the curved strip portion 801 along the stacking direction is 0.9μm~1.2μm, the diameter of the cylindrical portion 802 is 50μm~60μm, and the size of the cylindrical portion 802 along the stacking direction is 0.9μm~1.2μm.

[0035] The detector coupling layer 8 includes a coupling lower layer, a coupling middle layer and a coupling upper layer stacked from bottom to top. The coupling lower layer is an InP coupling lower layer or an InAlGaAs coupling lower layer with P-type modulation doping. The P-type doping concentration is 4×10 18 cm -3 Up to 9×10 18 cm -3 The coupling middle layer is used as the contact layer, which is an InGaAs coupling middle layer with P-type modulation doping, and the P-type doping concentration is 1×10 19 cm -3 Up to 2×10 19 cm -3 The size along the stacking direction is 0.2μm ~0.4μm, the coupling upper layer is the second upper electrode layer, and the coupling upper layer includes a second titanium layer and a second gold layer stacked in sequence from bottom to top, wherein the size of the second titanium layer along the stacking direction is 50 nm ~100nm, and the size of the second gold layer along the stacking direction is not less than 300nm.

[0036] It can be seen that in the embodiment of the present application, the laser ridge layer 7 and the detector coupling layer 8 are specially designed and well isolated, and can achieve optical coupling less than 1 / 100, thereby realizing power monitoring.

[0037] Preferably, in one embodiment of the present application, the lower electrode layer 1 adopts a double-layer structure, and has the following two construction methods: one is that the lower electrode layer 1 includes a third gold layer and a third titanium layer stacked in sequence from bottom to top; the other is that the lower electrode layer 1 includes a third gold layer and a gold-germanium-nickel layer stacked in sequence from bottom to top. It should be noted that, in this embodiment, the size of the third gold layer along the stacking direction is not less than 300nm, the size of the third titanium layer or the gold-germanium-nickel layer along the stacking direction is not less than 40nm, and the third gold layer, the third titanium layer or the gold-germanium-nickel layer must be flat and smooth.

[0038] The substrate layer 2 is located on the lower electrode layer 1 , and the substrate layer 2 is a GaAs substrate layer 2 or an InP substrate layer 2 that has been subjected to N-type modulation doping. The size of the substrate layer 2 along the stacking direction is 100 μm to 120 μm.

[0039] The lower cover layer 3 is arranged on the substrate layer 2. The lower cover layer 3 is an InP lower cover layer 3 or an AlGaAs lower cover layer 3 that has been modulated doped with N-type. The N-type doping concentration is 2×10 18 cm -3 , the size of the lower cover layer 3 along the stacking direction is not less than 1.6 μm.

[0040] The lower waveguide layer 4 is disposed on the lower cover layer 3. The lower waveguide layer 4 is an InGaAsP waveguide layer or an AlGaInAs waveguide layer, and the unintentional doping concentration is less than 1×10 17 cm -3 The size of the lower waveguide layer 4 along the stacking direction is not less than 0.5 μm, the refractive index of the lower waveguide layer 4 gradually increases from bottom to top, satisfies the e-index distribution, and the maximum refractive index does not exceed 3.55.

[0041] The multi-quantum well layer 5 is disposed on the lower waveguide layer 4. The multi-quantum well layer 5 is an InGaAs multi-quantum well layer 5 or an InGaAsP multi-quantum well layer 5. The unintentional doping concentration is less than 1×10 17 cm -3 The size of the multi-quantum well layer 5 along the stacking direction is 10nm~120nm, the multi-quantum well layer 5 includes 1~9 quantum wells, the well layer thickness is 3nm~9nm, and the barrier layer thickness is 5nm~12nm.

[0042] The upper waveguide layer 6 is located on the multi-quantum well layer 5. The upper waveguide layer 6 is an InGaAsP waveguide layer or an AlGaInAs waveguide layer, and the unintentional doping concentration is less than 1×10 17 cm -3 The size of the upper waveguide layer 6 along the stacking direction is not less than 0.9 μm, the refractive index of the upper waveguide layer 6 gradually decreases from bottom to top, satisfies the hyperbolic function distribution, and the minimum refractive index is not less than 2.9.

[0043] The insulating filling layer 9 is disposed on the upper waveguide layer 6 , and the insulating filling layer 9 is a silicon oxide layer or a silicon nitride layer.

[0044] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0045] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A semiconductor laser with built-in power monitoring, characterized in that: The invention comprises a lower electrode layer, a substrate layer, a lower cover layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a laser ridge stripe layer, a detector coupling layer and an insulating filling layer. The lower electrode layer, the substrate layer, the lower cover layer, the lower waveguide layer, the multi-quantum well layer and the upper waveguide layer are sequentially stacked from bottom to top. The laser ridge stripe layer, the detector coupling layer and the insulating filling layer are all arranged on the upper waveguide layer. The detector coupling layer and the laser ridge stripe layer are arranged at intervals. The insulating filling layer wraps the laser ridge stripe layer and the detector coupling layer partially, so that the first upper electrode layer at the upper end of the laser ridge stripe layer and the second upper electrode layer at the upper end of the detector coupling layer are exposed. The detector coupling layer is electrically isolated from the laser ridge stripe layer, and optical coupling is established.

2. The semiconductor laser with built-in power monitoring according to claim 1, characterized in that: The laser ridge layer includes a ridge lower layer, a ridge middle layer and a ridge upper layer stacked in sequence from bottom to top, the ridge lower layer is an InP ridge lower layer or an InAlGaAs ridge lower layer that has undergone P-type modulation doping, the ridge middle layer is an InGaAs ridge middle layer that has undergone P-type modulation doping, the ridge upper layer is the first upper electrode layer, and the ridge upper layer includes a first titanium layer and a first gold layer that are stacked in sequence from bottom to top.

3. The semiconductor laser with built-in power monitoring according to claim 2, characterized in that: The size of the laser ridge layer along a first direction perpendicular to the stacking direction is 150 μm to 4000 μm, the size of the laser ridge layer along a second direction perpendicular to the stacking direction is 2 μm to 100 μm, the first direction is perpendicular to the second direction, and the size of the laser ridge layer along the stacking direction is 0.9 μm to 1.2 μm.

4. The semiconductor laser with built-in power monitoring according to claim 1, characterized in that: The detector coupling layer includes a curved strip portion and a cylindrical portion, wherein the first end of the curved strip portion is close to the laser ridge layer, the second end of the curved strip portion is bent and extended in a direction away from the laser ridge layer, and the second end of the curved strip portion is connected to the cylindrical portion.

5. The semiconductor laser with built-in power monitoring according to claim 4, characterized in that: The size of the curved strip-shaped portion along a first direction perpendicular to the stacking direction is 20μm~30μm, the size of the curved strip-shaped portion along a second direction perpendicular to the stacking direction is 2μm~3μm, the first direction is perpendicular to the second direction, the size of the curved strip-shaped portion along the stacking direction is 0.9μm~1.2μm, the diameter of the cylindrical portion is 50μm~60μm, and the size of the cylindrical portion along the stacking direction is 0.9μm~1.2μm.

6. The semiconductor laser with built-in power monitoring according to claim 4, characterized in that: The detector coupling layer includes a coupling lower layer, a coupling middle layer and a coupling upper layer stacked in sequence from bottom to top, the coupling lower layer is an InP coupling lower layer or an InAlGaAs coupling lower layer that has been subjected to P-type modulation doping, the coupling middle layer is an InGaAs coupling middle layer that has been subjected to P-type modulation doping, the coupling upper layer is a second upper electrode layer, and the coupling upper layer includes a second titanium layer and a second gold layer that are stacked in sequence from bottom to top.

7. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The lower electrode layer includes a third gold layer and a third titanium layer stacked in sequence from bottom to top, or the lower electrode layer includes a third gold layer and a gold-germanium-nickel layer stacked in sequence from bottom to top, the size of the third gold layer along the stacking direction is not less than 300nm, and the size of the third titanium layer or the gold-germanium-nickel layer along the stacking direction is not less than 40nm.

8. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The substrate layer is a GaAs substrate layer or an InP substrate layer that has been subjected to N-type modulation doping, and the size of the substrate layer along the stacking direction is 100 μm to 120 μm.

9. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The lower cover layer is an InP lower cover layer or an AlGaAs lower cover layer that has been subjected to N-type modulation doping, and the size of the lower cover layer along the stacking direction is not less than 1.6 μm.

10. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The lower waveguide layer is an InGaAsP waveguide layer or an AlGaInAs waveguide layer, the size of the lower waveguide layer along the stacking direction is not less than 0.5 μm, the refractive index of the lower waveguide layer gradually increases from bottom to top, and the maximum refractive index does not exceed 3.

55.

11. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The multi-quantum well layer is an InGaAs multi-quantum well layer or an InGaAsP multi-quantum well layer, the size of the multi-quantum well layer along the stacking direction is 10nm~120nm, the multi-quantum well layer includes 1~9 quantum wells, the well layer thickness is 3nm~9nm, and the barrier layer thickness is 5nm~12nm.

12. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The upper waveguide layer is an InGaAsP waveguide layer or an AlGaInAs waveguide layer, the size of the upper waveguide layer along the stacking direction is not less than 0.9 μm, the refractive index of the upper waveguide layer gradually decreases from bottom to top, and the lowest refractive index is not less than 2.

9.

13. The semiconductor laser with built-in power monitoring according to any one of claims 1 to 6, characterized in that: The insulating filling layer is a silicon oxide layer or a silicon nitride layer.

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