A vertical wedge-shaped pattern converter and its manufacturing method

Abstract

The present invention relates to the technical field of optoelectronic device processing, and specifically to a vertical wedge-shaped pattern spot converter and a manufacturing method thereof, S1, forming a patterned mask layer on a substrate, the patterned mask layer having a groove exposing the substrate, and one end of the groove is open; S2, obtaining a material layer of a vertical wedge-shaped structure in the groove by selective epitaxial growth; S3, removing the patterned mask layer; S4, manufacturing a ridge waveguide structure on the material layer to obtain a vertical wedge-shaped pattern spot converter. The method of the present invention is simple to operate, and can be implemented by using traditional semiconductor manufacturing processes, has high mass production feasibility, and can meet the process mass production requirements.

Description

Technical Field

[0001] The invention relates to the technical field of optoelectronic device processing, and in particular to a vertical wedge-shaped pattern spot converter and a manufacturing method thereof. Background Art

[0002] Photodetectors (PDs) are key devices with high speed and high quantum efficiency in optical communication systems. With the development of optical communication technology in recent years, the demand for high-bandwidth PDs has become increasingly high. For PDs with vertical incidence structures, the bandwidth is generally increased by reducing the thickness of the absorption layer, but this is accompanied by a decrease in quantum conversion efficiency, resulting in low device responsivity. To solve this problem, people have designed PDs with side-incident structures, namely waveguide photodetectors (WGPDs). Since the propagation direction of photogenerated carriers is perpendicular to the direction of light absorption, the bandwidth and responsivity can be designed independently. However, WGPDs also have a significant drawback: the size of the light spot in the optical fiber is about 10um, while the size of the light spot in the WGPD is less than 2um. Such a large difference in the size of the spot leads to large coupling losses when light is incident on the WGPD from the optical fiber, greatly reducing the light transmission efficiency.

[0003] In order to achieve efficient coupling between optical fiber and WGPD, people have proposed to use a spot converter to match the spot size of the optical fiber and the WGPD. The spot converter generally adopts a wedge-shaped structure design, which can be divided into a horizontal wedge-shaped spot converter and a vertical wedge-shaped spot converter according to the wedge plane. The horizontal wedge-shaped spot converter is simple to make and can be made using traditional photolithography technology, but the conversion efficiency in the vertical direction is still limited. The vertical wedge-shaped spot converter requires a three-dimensional structure to be made through plane processing technology, so its manufacturing process is very complicated and difficult, and it has a very broad application prospect.

[0004] To make vertical wedge-shaped spot converters, the processes currently used include grayscale exposure, dynamic etching, diffusion-limited etching, etc. Among them, grayscale lithography is the most effective, but it involves the production of grayscale photoresist, which is very difficult. Dynamic etching, diffusion-limited etching and other solutions are complex processes with low repeatability and are not suitable for mass production. Summary of the invention

[0005] The purpose of the present invention is to provide a vertical wedge-shaped pattern spot converter and a method for manufacturing the same, which is not only simple to operate but can also be implemented using traditional semiconductor manufacturing equipment, thus meeting the needs of mass production.

[0006] To achieve the above object, the technical solution of the present invention is a method for manufacturing a vertical wedge-shaped pattern spot converter, comprising the following steps:

[0007] S1. forming a patterned mask layer on a substrate, wherein the patterned mask layer has a groove exposing the substrate, and one end of the groove is open;

[0008] S2, obtaining a material layer with a vertical wedge-shaped structure in the groove by selective epitaxial growth;

[0009] S3, removing the patterned mask layer;

[0010] S4. Fabricate a ridge waveguide structure on the material layer to obtain a vertical wedge-shaped spot converter.

[0011] As one of the implementation modes, the patterned mask layer includes a rectangular area and two right-angled triangular areas that are mirror-symmetrical to each other and located in the same plane. The two right-angled triangular areas are located on the same side of the rectangular area and form the groove together with the rectangular area.

[0012] As one of the implementation modes, the long right-angled sides of the two right-angled triangle areas are arranged back to back, and the short right-angled sides are located on the rectangular area.

[0013] As one of the implementation modes, the distance between the two right-angled triangle areas is 20-30 um; the length of the short right-angled side of each right-angled triangle area is 120±5 um, and the length of the long right-angled side is 200±5 um.

[0014] As one of the implementation modes, the specific steps of forming a patterned mask layer on the substrate in step S1 are: first depositing a first mask layer on the substrate, then making a first photoresist pattern on the first mask layer, and then using the first photoresist pattern as a mask to etch the first mask layer, and then removing the first photoresist pattern to obtain the patterned mask layer.

[0015] As one of the implementation methods, the specific steps for making the first photoresist pattern are: spin coating photoresist on the first mask layer, and exposing and developing it, so that the first mask layer in the patterned mask layer area is covered by photoresist and the first mask layer in the remaining area is exposed.

[0016] As one of the implementation modes, the specific steps of obtaining a material layer with a vertical wedge-shaped structure in the groove by means of selective epitaxial growth in step S2 are as follows: placing the substrate with the patterned mask layer obtained in step S1 into a metal organic chemical vapor deposition chamber, first heating it to 550-650°C and baking it for 5-10 minutes, and then growing III-V compounds under N2 carrier gas conditions, thereby obtaining a material layer with a vertical wedge-shaped structure in the groove.

[0017] As one of the implementation methods, the specific steps of making the ridge waveguide structure on the material layer in step S4 are: first define a ridge waveguide pattern on the material layer by photolithography, then remove the material layer outside the ridge waveguide pattern, and then remove the ridge waveguide pattern to obtain the ridge waveguide structure.

[0018] As one of the implementation modes, the following step is further included after step S4: depositing a protective layer.

[0019] The present invention also provides a vertical wedge-shaped pattern spot converter, which is manufactured using any of the manufacturing methods described above.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention first forms a patterned mask layer on a substrate, and then epitaxially grows a waveguide material in a selective area. No epitaxial material is deposited on the surface of the patterned mask layer because the material cannot nucleate. The groove of the patterned mask layer exposes the substrate and one end is open, so a material layer with a vertical wedge-shaped structure grows. A ridge waveguide structure is then made on the material layer to obtain a vertical wedge-shaped pattern spot converter. The method of the present invention is simple to operate, and both the patterned mask layer and the ridge waveguide structure can be realized by using traditional semiconductor manufacturing processes, and has high mass production feasibility, which can meet the process mass production requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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.

[0023] Figure 1 A flow chart of a method for manufacturing a vertical wedge-shaped pattern spot converter provided by an embodiment of the present invention;

[0024] Figure 2 A top view of a patterned mask layer provided in an embodiment of the present invention;

[0025] Figure 3 A top view of a vertical wedge-shaped structure after selective epitaxial growth provided by an embodiment of the present invention;

[0026] Figure 4 for Figure 3 AA' direction cross-sectional view;

[0027] Figure 5 for Figure 3 BB' direction cross-sectional view;

[0028] Figure 6 A three-dimensional image of a vertical wedge-shaped structure after selective epitaxial growth provided by an embodiment of the present invention;

[0029] Figure 7 A scanning electron microscope image of a vertical wedge-shaped structure after selective epitaxial growth provided by an embodiment of the present invention;

[0030] In the figure: 1. substrate; 2. patterned mask layer; 3. material layer. DETAILED DESCRIPTION

[0031] 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.

[0032] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0034] like Figure 1-Figure 7 As shown, this embodiment provides a method for manufacturing a vertical wedge-shaped pattern spot converter, comprising the following steps:

[0035] S1, forming a patterned mask layer 2 on a substrate 1, wherein the patterned mask layer 2 has a groove exposing the substrate 1, and one end of the groove is open;

[0036] S2, obtaining a material layer 3 with a vertical wedge-shaped structure in the groove by selective epitaxial growth;

[0037] S3, removing the patterned mask layer 2;

[0038] S4, making a ridge waveguide structure on the material layer 3 to obtain a vertical wedge-shaped spot converter.

[0039] In this embodiment, a patterned mask layer 2 is first formed on the substrate 1, and then a waveguide material is selectively epitaxially grown. No epitaxial material is deposited on the surface of the patterned mask layer 2 because the material cannot nucleate. The groove of the patterned mask layer 2 exposes the substrate 1 and one end is open, so a material layer 3 with a vertical wedge-shaped structure grows. A ridge waveguide structure is then made on the material layer 3 to obtain a vertical wedge-shaped pattern spot converter. The method of this embodiment is simple to operate, and both the patterned mask layer 2 and the ridge waveguide structure can be realized by using traditional semiconductor manufacturing processes, and has high mass production feasibility and can meet process mass production requirements.

[0040] In some embodiments, the patterned mask layer 2 includes a rectangular area and two right-angled triangle areas that are mirror-symmetrical to each other in the same plane, and the two right-angled triangle areas are located on the same side of the rectangular area and form the groove with the rectangular area. One end of the two right-angled triangle areas is an integral structure with the rectangular area, and there is a certain distance between the other ends of the two right-angled triangle areas, so that a groove is formed on the substrate 1 that exposes the substrate 1 and is horizontally open at one end and closed at the other end. When the material layer 3 is epitaxially grown, the growth gas at the open end of the groove diffuses through the open end to the surrounding mask-free area, and the grown material layer is thinner, while the growth gas at the closed end diffuses and accumulates, and the grown material layer is thicker, so that the slope of the material layer 3 in the groove is more obvious, thereby obtaining a material layer 3 with a vertical wedge structure.

[0041] Furthermore, the long right-angled sides of the two right-angled triangle areas are arranged back to back, and the short right-angled sides are located on the rectangular area. Figure 2 and Figure 3 As shown, the short right sides of the two right-angled triangle areas are located on the long side of the rectangular area, and the length of the long side of the rectangular area is equal to the sum of the length of the short right sides of the two right-angled triangle areas and the distance between the two right-angled triangle areas.

[0042] Optimally, the distance (Wo) between the two right-angled triangle areas is 20-30 um; the length of the short right-angled side (Wm) of each right-angled triangle area is 120±5 um, and the length of the long right-angled side (L) is 200±5 um.

[0043] In this embodiment, a material layer 3 is deposited in the groove of the patterned mask layer 2 by selective epitaxial growth. The obtained material layer 3 of the vertical wedge-shaped structure is as shown in FIG. Figure 4 and Figure 6 As shown. The vertical wedge-shaped structure near the edge of the patterned mask layer 2 in the groove has a peak due to the selective growth effect, as shown in FIG. Figure 5 shown.

[0044] To refine the above embodiment, the specific steps of forming the patterned mask layer 2 on the substrate 1 in step S1 are: first depositing a first mask layer on the substrate 1, then making a first photoresist pattern on the first mask layer, then using the first photoresist pattern as a mask to etch the first mask layer, and then removing the first photoresist pattern to obtain the patterned mask layer 2. In this embodiment, the first mask layer adopts a silicon dioxide film, which has good chemical stability and a high etching selectivity, and its thickness is 150nm±15nm. Specifically, plasma enhanced chemical vapor deposition (PECVD) technology can be used to achieve uniform and high-quality thin film deposition; when etching and removing the first mask layer, reactive ion etching (RIE) technology can be used to help achieve accurate pattern transfer, and the etching gas is Ar2:CHF3, and the gas flow rate is 25±2sccm.

[0045] Furthermore, the specific steps of making the first photoresist pattern are: spin-coating photoresist on the first mask layer, and performing exposure and development, so that the first mask layer in the patterned mask layer 2 area is covered by the photoresist, and the first mask layer in the remaining area is exposed. Among them, the photoresist preferably uses AZ series positive photoresist, such as AZ5214, AZ6130, etc., which has good resolution and adhesion, and the number of rotations of the uniform coating during spin coating is 3000 rpm; exposure is performed using an MA6 contact exposure machine, the exposure time is 7s, to ensure that the photoresist can fully absorb light energy and undergo chemical reactions, and the development time is 60s, to ensure that the photoresist in the exposed area will be dissolved and removed, while the photoresist in the unexposed area will be retained, forming a pattern corresponding to the patterned mask layer 2.

[0046] To refine the above embodiment, the specific steps of obtaining a material layer with a vertical wedge-shaped structure in the groove by selective epitaxial growth in step S2 are: placing the substrate 1 with the patterned mask layer 2 obtained in step S1 into a metal organic chemical vapor deposition chamber, first heating it to 550-650°C and baking it for 5-10 minutes, and then growing III-V compounds under N2 carrier gas conditions, thereby obtaining a material layer 3 with a vertical wedge-shaped structure in the groove.

[0047] In this embodiment, the material layer 3 includes a lower confinement layer, a core layer, and an upper confinement layer grown sequentially from bottom to top. The material layer 3 can be made of InP / InGaAsP / InP and obtained by MOCVD (metal organic chemical vapor deposition) technology, specifically, first growing an InP lower confinement layer, then growing an InGaAsP core layer, and finally growing an InP upper confinement layer; in step S5, inductively coupled plasma etching (ICP) can be used to remove the material layer 3 outside the ridge waveguide pattern.

[0048] To refine the above embodiment, the specific steps of making the ridge waveguide structure on the material layer 3 in step S4 are: first, define a ridge waveguide pattern on the material layer 3 by photolithography, then remove the material layer 3 outside the ridge waveguide pattern, and then remove the ridge waveguide pattern to obtain the ridge waveguide structure. In this embodiment, reactive ion etching (RIE) technology can be used to remove the patterned mask layer 2 and the ridge waveguide pattern.

[0049] Among them, the specific steps of defining the ridge waveguide pattern on the material layer 3 by photolithography are: first depositing a second mask layer, then making a second photoresist pattern on the second mask layer, and then using the second photoresist pattern as a mask to etch the second mask layer, and then removing the second photoresist pattern to obtain the ridge waveguide pattern.

[0050] The specific steps of making the second photoresist pattern are: uniformly coating the photoresist on the second mask layer, and performing exposure and development, so that the second mask layer in the ridge waveguide pattern area is covered by the photoresist, and the second mask layer in the remaining area is exposed. In this embodiment, the second mask layer is made of silicon dioxide film with a thickness of 300±15nm, which can be formed by plasma enhanced chemical vapor deposition (PECVD) technology; when etching and removing the second mask layer, reactive ion etching (RIE) technology can be used, and the etching gas is Ar2:CHF3, and the gas flow rate is 25±2sccm.

[0051] The above embodiment is optimized, and the following step is further included after step S4: depositing a protective layer. By depositing a protective layer on the surface of the ridge waveguide structure, the epitaxial material can be protected, and the stability and reliability of the device can be further improved. The protective layer is made of a silicon dioxide film, which has good insulation and chemical stability, has a thickness of 300 nm, and can be formed by plasma enhanced chemical vapor deposition (PECVD) technology.

[0052] This embodiment also provides a vertical wedge-shaped pattern spot converter, which is manufactured using any of the manufacturing methods described above.

[0053] The above-mentioned production method is described below through a specific embodiment.

[0054] This embodiment provides a method for manufacturing a vertical wedge-shaped pattern spot converter, comprising the following steps:

[0055] S1, depositing a first mask layer on substrate 1 using PECVD technology; the first mask layer uses a silicon dioxide film with a thickness of 150 nm;

[0056] S2, spin-coating AZ5214 positive photoresist on the first mask layer at 3000 rpm, using MA6 contact exposure machine for exposure time of 7s and development time of 60s to obtain a first photoresist pattern; then using the first photoresist pattern as a mask, using RIE to etch the first mask layer, using Ar2:CHF3 as etching gas, and a gas flow rate of 25sccm, and then removing the first photoresist pattern to obtain a patterned mask layer 2;

[0057] The patterned mask layer 2 includes a rectangular area and two right-angled triangular areas in the same plane, which are mirror-symmetrical to each other. The two right-angled triangular areas are located on the same side of the rectangular area and form a groove with one end open to expose the substrate 1, such as Figure 2 As shown, the long right-angled sides of the two right-angled triangle areas are arranged back to back, the short right-angled sides are located on the rectangular area, and the distance (Wo) between the two right-angled triangle areas is 25um; the length (Wm) of the short right-angled side of each right-angled triangle area is 120um, and the length (L) of the long right-angled side is 200um;

[0058] S3, placing the substrate 1 with the patterned mask layer 2 into a metal organic chemical vapor deposition chamber, first heating to 600° C. and baking for 5 min, then growing III-V compounds under N2 carrier gas conditions, thereby obtaining a material layer 3 with a vertical wedge-shaped structure in the groove; the material layer 3 is a lower limiting layer / core layer / upper limiting layer of InP / InGaAsP / InP;

[0059] S4, removing the patterned mask layer 2 by RIE etching;

[0060] S5, depositing a second mask layer on the material layer 3 of the vertical wedge-shaped structure, wherein the second mask layer is made of a silicon dioxide film with a thickness of 300 nm;

[0061] S6. Evenly coat the second mask layer with photoresist, expose and develop it to obtain a second photoresist pattern. Then, use the second photoresist pattern as a mask to etch the second mask layer using RIE. The etching gas is Ar2:CHF3 and the gas flow rate is 25sccm. Then, remove the second photoresist pattern to obtain a ridge waveguide pattern.

[0062] S7, removing the material layer 3 outside the ridge waveguide pattern by ICP etching;

[0063] S8. Use RIE etching to remove the ridge waveguide pattern to obtain a ridge waveguide structure; deposit a protective layer on the surface of the ridge waveguide structure to obtain a vertical wedge-shaped pattern converter; the protective layer uses a silicon dioxide film with a thickness of 300nm.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a vertical wedge-shaped pattern spot converter, characterized in that: The steps include: S1. forming a patterned mask layer on a substrate, wherein the patterned mask layer has a groove exposing the substrate, and one end of the groove is open; S2, obtaining a material layer with a vertical wedge-shaped structure in the groove by selective epitaxial growth; S3, removing the patterned mask layer; S4. Fabricate a ridge waveguide structure on the material layer to obtain a vertical wedge-shaped spot converter.

2. The method according to claim 1, characterized in that: The patterned mask layer includes a rectangular area and two right-angled triangle areas that are mirror-symmetrical to each other in the same plane. The two right-angled triangle areas are located on the same side of the rectangular area and form the groove together with the rectangular area.

3. The method according to claim 2, characterized in that: The long right-angled sides of the two right-angled triangle areas are arranged back to back, and the short right-angled sides are located on the rectangular area.

4. The method according to claim 3, characterized in that: The distance between the two right-angled triangle areas is 20-30 um; the length of the short right-angled side of each right-angled triangle area is 120±5 um, and the length of the long right-angled side is 200±5 um.

5. The method according to claim 1, wherein: The specific steps of forming a patterned mask layer on the substrate in step S1 are: first depositing a first mask layer on the substrate, then making a first photoresist pattern on the first mask layer, then using the first photoresist pattern as a mask to etch the first mask layer, and then removing the first photoresist pattern to obtain the patterned mask layer.

6. The method according to claim 5, characterized in that: The specific steps of making the first photoresist pattern are: spin coating photoresist on the first mask layer, and performing exposure and development, so that the first mask layer in the patterned mask layer area is covered by the photoresist, and the first mask layer in the remaining area is exposed.

7. The method according to claim 1, characterized in that: The specific steps of obtaining a material layer with a vertical wedge-shaped structure in the groove by selective epitaxial growth in step S2 are as follows: placing the substrate with the patterned mask layer obtained in step S1 into a metal organic chemical vapor deposition chamber, first heating it to 550-650°C and baking it for 5-10 minutes, and then growing III-V compounds under N2 carrier gas conditions, thereby obtaining a material layer with a vertical wedge-shaped structure in the groove.

8. The method according to claim 1, characterized in that: The specific steps of making the ridge waveguide structure on the material layer in step S4 are: firstly define a ridge waveguide pattern on the material layer by photolithography, then remove the material layer outside the ridge waveguide pattern, and then remove the ridge waveguide pattern to obtain the ridge waveguide structure.

9. The method according to claim 1, characterized in that: The step S4 is followed by the following step: depositing a protective layer.

10. A vertical wedge-shaped pattern converter, characterized in that: The vertical wedge-shaped pattern spot converter is manufactured by the manufacturing method described in any one of claims 1 to 9.

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