CN101393945A - All-silicon waveguide photoelectric converter and manufacturing method thereof - Google Patents

Abstract

The invention relates to the technical field of photoelectric converters, and discloses a 1.55-band all-silicon waveguide photoelectric conversion device compatible with a complementary metal-oxide layer-semiconductor (CMOS) process, wherein light absorption is achieved by implanting Si ions into Si to form a network The deep energy level defect of compound is carried out, so as to break through the restriction of the 1.12eV bandgap width of Si optoelectronic devices; the device structure is on the Si-based SOI substrate, with the straight waveguide implanted with Si ions as the intrinsic region (i) , with n-type and p-type doping regions (n, p) on the left and right, forming a lateral p-i-n structure on the surface layer; the curved waveguide is used as the signal input part, the straight waveguide is used as the light absorption part, and the two sides of the straight waveguide Distributed Bragg reflection gratings are set at the end to make the optical signal resonate in the straight waveguide to enhance light absorption. The invention also discloses a manufacturing method of an all-silicon waveguide type photoelectric conversion device, which can realize the integration of a communication signal receiving device and a microelectronic chip on Si.

Description

All-silicon waveguide photoelectric converter and manufacturing method thereof

technical field

The invention relates to the technical field of photoelectric converters, in particular to a 1.55-band all-silicon waveguide photoelectric converter compatible with a complementary metal-oxide layer-semiconductor (CMOS) process and a manufacturing method thereof.

Background technique

With the development of high-density and large-capacity data transmission and computing, the advantages of integrating optoelectronics and microelectronics on a chip are becoming more and more obvious, and the demand is becoming more and more urgent. It is of great importance to the development of our national economy, national security and scientific progress play an important supporting role. For this reason, a large number of optical passive devices have been developed on Si-based SOI waveguides by using the mature Si process and the transparency of Si in the communication band. However, the research progress on Si-based optical active devices is slow. The reason is not only the low optical absorption and transition rate due to the indirect bandgap of Si, which does not absorb light waves with a wavelength greater than 1 μm, but also the structure is not easy to Integrated with Si waveguides.

Si-based photodetectors are devices that receive optical signals and convert them into electrical signals in Si-based optoelectronic integration. For light waves with a wavelength of less than 1 μm, Si-based photodetectors have fast response, high detection sensitivity, small dark current and frequency. The characteristics of bandwidth, and it is easy to form a hybrid integrated optoelectronic circuit with a field effect transistor (FET) and a heterojunction bipolar transistor (HBT) to jointly complete the functions of light detection and light signal amplification. It is indispensable in a monolithic integrated system. part.

In the communication band, Ge is mainly used as the active material of Si-based photodetectors, because Ge has the advantages of good light absorption characteristics, high carrier mobility, and easy compatibility with Si process. However, the lattice mismatch between Ge and Si is as high as 4%, and there are certain difficulties in direct growth; secondly, the usual discrete devices are used to detect optical signals perpendicular to the surface of the film, and cannot be integrated with planar optical waveguides; thirdly, in discrete In the device, light absorption requires intrinsic layer thickness and carrier drift requires intrinsic layer thickness to be contradictory; fourth, the process used in discrete devices is not compatible with complementary metal-oxide-semiconductor (CMOS) processes, and thus cannot be compatible with microelectronics integrated. In response to these shortcomings, many researchers have developed lateral devices connected to waveguides, which can be divided into two categories: one is the pn or pin structure that was stacked up and down by epitaxial growth in the early stage (H.Temkin, et.al ., "G _x Si _1-x strained-layer superlattice waveguide photo-detectors operating near 1.3μm", AppliedPhysics Letters, 48:963-65, 1986), its advantage is that it can copy the growth of various materials in vertical devices to meet the lateral The shortcoming is that it is poorly compatible with CMOS, and its top metal electrode absorbs the light signal strongly and causes loss; the other type is the recently developed lateral pin structure, which uses ion implantation to form a double pin structure in Si. Vacancy complex (divacancy complex) defects, valence band electrons jump to deep energy levels after absorbing photons (defect light absorption) (EVMonakhov, et.al., "Divacancy annealing in Si: Influence of hydrogen", Physical Review B, 69 : 153202, 2006), and release electrons after saturation. Its biggest advantage is compatibility with CMOS and integration with optoelectronics. Although the efficiency of defect light absorption is low, it can be compensated by extending the absorption waveguide. The research team of the Department of Engineering Physics, McMaster University in Canada used the second type of lateral pin structure to prepare a photodetector with a responsivity of 9 mA/W at a wavelength of 1.55 μm (JDB Bradley, et.al., "Silicon waveguide-integrated optical power monitor with enhanced sensitivity at 1550nm”, Applied Physics Letters, 86: 241103, 2005); the Lincoln Laboratory of MIT in the United States refined the waveguide of the former, which shortened the transit time of photogenerated carriers and obtained better results. The device works The wavelength is 1.27-1.74μm, the responsivity at 1.55μm is 800mA/W, and the 3dB bandwidth is 10-20GHz (MWGleis, et al., "CMOS-compatible all-Si high-speed waveguidephotodiodes with high responsivity in near-infrared communication band ", IEEE Photonics Technology Letters, 19(3):152-54, 2007).

Although Si-based photodetectors have made great progress, there are still some problems and room for improvement. First of all, the device is too long (about 1mm). For a waveguide with a cross-sectional area of 0.5×0.22 square microns, it is not easy to make the device by extending 2000 times on the Si sheet; secondly, the electron transport mechanism is unknown, and the Si waveguide absorbs in principle It is due to the double-vacancy complex defects caused by Si ⁺ ion implantation, and the valence band electrons absorb photons and jump to the deep energy level of the defect, but it is not clear how the electrons are transported from the deep energy level to the electrode, which makes the device preparation very interesting. blindness.

Contents of the invention

(1) Technical problems to be solved

In view of this, an object of the present invention is to provide an all-silicon waveguide photoelectric conversion device, especially an all-silicon waveguide photoelectric conversion device compatible with CMOS technology in the 1.55 micron band, which breaks through Si photoelectricity by means of deep-level light absorption. The detector is constrained by the 1.12eV forbidden band width.

Another object of the present invention is to provide a method for manufacturing an all-silicon waveguide-type photoelectric conversion device, especially a method for manufacturing an all-silicon waveguide-type photoelectric conversion device compatible with a CMOS process in the 1.55 micron band, so that communication signals can be realized on Si Integration of receiving devices with microelectronic chips.

(2) Technical solution

To achieve the above-mentioned purpose, the present invention provides a method for manufacturing an all-silicon waveguide photoelectric conversion device, the method comprising the following steps:

forming a Si-based SOI substrate comprising a Si thin layer 3;

Etching the Si thin layer 3 into a straight waveguide 3 and a curved waveguide 8 by dry etching or wet etching;

Implanting silicon ions (Si ⁺ ), silver ions (Ag ⁺ ) or hydrogen ions (H ⁺ ) on the surface of the straight waveguide 3 by ion implantation, and annealing to form complex defects with deep energy levels;

Using an etching method to prepare distributed Bragg reflection gratings at both ends of the straight waveguide 3, so that the straight waveguide 3 becomes a resonant cavity;

Using ion implantation or diffusion, implant or diffuse group III ions on one side of the straight waveguide 3 and anneal to form p-type doped region 4, and implant or diffuse group V ions on the other side of the straight waveguide 3 and anneal to form n Type doped region 5, thus forming a lateral p-i-n structure on the surface layer of the substrate.

In the above solution, the SOI substrate is composed of Si substrate 1, SiO ₂ lower cladding layer 2, and Si thin layer 3 arranged in sequence from bottom to top.

In the above solution, the p-type doped region 4 and the n-type doped region 5 are respectively provided with Al or Al alloy electrodes locally prepared by metal evaporation.

In the above solution, the curved waveguide 8 is tangent to the straight waveguide, and the outer port of the curved waveguide 8 is the light wave incident end, and the light wave is merged into the straight waveguide resonant cavity 3 through the curved waveguide 8 .

In the above solution, the distributed Bragg reflection grating has periodic bar-shaped grooves, thereby forming high reflection for communication light waves.

In the above solution, the cavity length of the resonant cavity 3 between the two reflective gratings satisfies an integer multiple of the communication wavelength.

In the above solution, the wavelength of the communication light wave is in the 1.55 micron band.

For achieving above-mentioned another purpose, the present invention provides a kind of all-silicon waveguide type photoelectric converter, has the Si base SOI substrate that comprises Si thin layer 3, and this photoelectric converter comprises:

A straight waveguide 3 and a curved waveguide 8, the straight waveguide 3 and the curved waveguide 8 are formed by dry etching or wet etching the Si thin layer 3, wherein: a distributed Bragg reflection grating is arranged at both ends of the straight waveguide 3 so that The straight waveguide 3 becomes a resonant cavity, and Si ions are implanted on the surface of the straight waveguide 3 and annealed to form deep level defects;

The p-type doped region 4 formed on one side of the straight waveguide 3 and the n-type doped region 5 formed on the other side of the straight waveguide 3 form a lateral p-i-n structure on the Si surface layer.

In the above solution, the p-type doped region 4 is formed by implanting or diffusing boron ions B ⁺ on one side of the straight waveguide 3 and annealing, and the n-type doped region 5 is formed by implanting B+ on the other side of the straight waveguide 3 Or diffuse phosphorus ions P ⁺ to form.

In the above solution, the SOI substrate is composed of Si substrate 1, SiO ₂ lower cladding layer 2 and Si thin layer 3 arranged in sequence from bottom to top.

In the above solution, the p-type doped region 4 and the n-type doped region 5 respectively have Al or Al alloy electrodes locally prepared by metal evaporation.

In the above solution, the curved waveguide 8 is tangent to the straight waveguide, and the outer port of the curved waveguide 8 is the light wave incident end, and the light wave is merged into the straight waveguide resonant cavity 3 through the curved waveguide 8 .

In the above solution, the bending radius of the curved waveguide 8 is proportional to the signal strength of the returning light wave.

In the above solution, the distributed Bragg reflection grating has periodic bar-shaped grooves, thereby forming high reflection for communication light waves.

In the above solution, the cavity length of the resonant cavity 3 between the two reflective gratings satisfies an integer multiple of the communication wavelength.

In the above solution, the wavelength of the communication light wave is in the 1.55 micron band.

(3) Beneficial effects

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

1. Using the present invention, the curved waveguide can be used as the entrance of the photoelectric converter, the curved waveguide is tangent to the straight waveguide, the light wave is input into the straight waveguide resonant cavity through the curved waveguide, and the light wave transmitted from the straight waveguide resonant cavity to the curved waveguide is seldom , whose strength is proportional to the bending waveguide. Therefore, the "r"-shaped device combined by the straight waveguide resonator and the curved waveguide has an approximate one-way light-passing characteristic.

2. Utilizing the present invention, a distributed Bragg (Bragg) high-reflection grating can be arranged at both ends of the straight waveguide, and according to the theory of photonic crystal high-order forbidden band and dielectric periodic field, etch or corrode tiny periodic strips on the Si waveguide Groove, so as to form a high reflection of the light wave in the 1.55 micron band;

3. Using the present invention, a resonant cavity can be formed between two distributed Bragg high-reflection gratings, and the cavity length of the resonant cavity satisfies an integer multiple of the communication wavelength (such as 1.55 microns) to form a resonance.

4. With the present invention, the light absorption path (along the waveguide direction) can be separated from the carrier drift path (perpendicular to the waveguide direction), and the response time can be accelerated while improving the quantum efficiency.

5. Using the present invention, the optical signal in the waveguide can be directly detected, thereby forming a lossless connection with the planar light wave circuit and forming a planar integrated circuit;

6. Utilizing the present invention, the preparation of photodetection devices can be compatible with CMOS technology, so that they can be integrated with microelectronic chips.

Description of drawings

1 is a cross-sectional view of a vertical waveguide of an all-silicon waveguide type photoelectric conversion device structure of the present invention; and

Fig. 2 is a top view of the vertical waveguide of the all-silicon waveguide photoelectric conversion device structure of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in combination with specific examples and with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a vertical waveguide of an all-silicon waveguide photoelectric conversion device structure provided by the present invention. Preferably, the all-silicon waveguide photoelectric conversion device is suitable for a 1.55 micron waveband. The whole device is prepared on Si-based SOI substrate, from bottom to top are Si substrate 1, SiO ₂ lower cladding layer 2 and Si ridge waveguide 3; the left side of the waveguide is p-type doped region 4 and Al or Al alloy electrode 6. On the right side of the waveguide are n-type doped regions 5 and Al or Al alloy electrodes 7 .

Fig. 2 is the top view of the vertical waveguide of the 1.55 micron band all-Si waveguide photoelectric conversion device structure of the present invention, the waveguide is composed of a curved waveguide 8 and a straight waveguide 3, and the two ends of the straight waveguide 3 are distributed Bragg gratings (Distributed Bragg Raster, DBR for short) ) 9, 10, there is a resonant cavity between the reflective gratings, so that the straight waveguide 3 is a resonant cavity, the length of the resonant cavity is an integer multiple of the resonant wavelength, and the optical wave is resonated in the resonant cavity to strengthen the defect light absorption and shorten the device size; The two sides of the straight waveguide 3 are the same as in Fig. 1, the left side of the waveguide is the p-type doped region 4 and the Al or Al alloy electrode 6, and the right side of the waveguide is the n-type doped region 5 and the Al or Al alloy electrode 7, so that A lateral p-i-n structure is formed on the Si plane. This lateral p-i-n structure can separate the light absorption path (along the waveguide direction) from the carrier drift path (perpendicular to the waveguide direction), which can speed up the response time while improving the quantum efficiency.

Etch the Si thin layer 3 into a straight waveguide 3 and a curved waveguide 8 by dry etching or wet etching; further etch or etch the distributed Bragg reflection gratings 9 and 10 at both ends of the Si thin layer 3 to make the straight waveguide 3 and the curved waveguide 8; The waveguide 3 is a resonant cavity. In addition, the curved waveguide 8 is tangent to the straight waveguide 3 and constitutes an "r" shaped waveguide with the straight waveguide. waveguide. Therefore, it can be said that the "r"-shaped waveguide has approximate unidirectional light wave transmission characteristics; on the other hand, since the signal input does not pass through the DBR, a DBR with high reflectivity can be prepared to make the resonance characteristics better.

Use ion (such as boron ion B ⁺ ) implantation or diffusion method, implant or diffuse Group III ions on one side of the waveguide 3 and anneal to form a p-type doped region 4; and locally adopt the method of metal evaporation to prepare Al or Al alloy electrode 6;

Using ion (such as phosphorus ion P ⁺ ) implantation or diffusion method, implant or diffuse group V ions on the other side of the waveguide 3 and anneal to form an n-type doped region 5; and locally adopt the method of metal evaporation to prepare Al or Al alloy electrode 7, thereby forming a lateral pin structure on the Si plane;

Implant Si ⁺ ions, silver ions Ag ⁺ or hydrogen ions (H ⁺ ) into the straight waveguide 3, and form divacancy complex defects after annealing, and the valence band electrons are excited by photons (such as 1.55 micron band) Transition to the defect deep energy level (defect light absorption), and then, electrons jump and migrate on the deep energy level; or, the electrons on the deep energy level are excited by the secondary light and sent into the conduction band, thereby forming a secondary light Excited defect photoconductivity.

It should be noted that the specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to To limit the present invention, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (16)

1. A method for manufacturing an all-silicon waveguide photoelectric conversion device, characterized in that the method comprises the following steps: forming a Si-based SOI substrate comprising a Si thin layer (3); Etching the Si thin layer (3) into a straight waveguide (3) and a curved waveguide (8) by dry etching or wet etching; Using the method of ion implantation, silicon ions (Si ⁺ ), silver ions (Ag ⁺ ) or hydrogen ions (H ⁺ ) are implanted on the surface of the straight waveguide (3), and annealed to form complex defects with deep energy levels ; Using an etching method, preparing distributed Bragg reflection gratings (9, 10) at both ends of the straight waveguide (3), so that the straight waveguide (3) becomes a resonant cavity; Using ion implantation or diffusion, implant or diffuse group III ions on one side of the straight waveguide (3) and anneal to form a p-type doped region (4), and implant or diffuse group V on the other side of the straight waveguide (3) ions and annealed to form an n-type doped region (5), thereby forming a lateral p-i-n structure on the surface layer of the substrate. 2. The method for manufacturing an all-silicon waveguide photoelectric conversion device according to claim 1, characterized in that the SOI substrate is composed of Si substrate (1), SiO ₂ lower cladding layer (2) arranged in sequence from bottom to top ), and Si thin layer (3). 3. The method for manufacturing an all-silicon waveguide photoelectric conversion device according to claim 1, characterized in that the p-type doped region (4) and the n-type doped region (5) are respectively arranged on it There are Al or Al alloy electrodes prepared locally by metal evaporation (6, 7). 4. The method for manufacturing an all-silicon waveguide photoelectric conversion device according to claim 1, characterized in that the curved waveguide (8) is tangent to the straight waveguide, and the outer port of the curved waveguide (8) is the light wave incident end, and the light wave The straight waveguide resonator (3) is merged into the straight waveguide resonant cavity (3) through the curved waveguide (8). 5. The method for manufacturing an all-silicon waveguide photoelectric conversion device according to claim 1, characterized in that, The distributed Bragg reflection grating has periodic strip grooves, so as to form high reflection for communication light waves. 6. The method for manufacturing an all-silicon waveguide photoelectric conversion device according to claim 5, characterized in that, The cavity length of the resonant cavity (3) between the two reflective gratings satisfies the integral multiple of the communication wavelength. 7. The method for manufacturing an all-silicon waveguide photoelectric conversion device according to claim 5 or 6, characterized in that, The communication light wave has a wavelength of 1.55 microns. 8. An all-silicon waveguide photoelectric converter having a Si-based SOI substrate comprising a Si thin layer (3), characterized in that the photoelectric converter comprises: A straight waveguide (3) and a curved waveguide (8), the straight waveguide (3) and the curved waveguide (8) are formed by dry etching or wet etching the Si thin layer (3), wherein: in the straight waveguide ( 3) Distributed Bragg reflection gratings (9, 10) are arranged at both ends so that the straight waveguide (3) becomes a resonant cavity, and Si ions are implanted on the surface of the straight waveguide (3) and annealed to form deep level defects; A p-type doped region (4) formed on one side of the straight waveguide (3) and an n-type doped region (5) formed on the other side of the straight waveguide (3) form a lateral p-i-n structure on the Si surface layer. 9. The all-silicon waveguide photoelectric converter according to claim 8, characterized in that the p-type doped region (4) is formed by implanting or diffusing boron ions B ⁺ on one side of the straight waveguide (3) and annealing The n-type doped region (5) is formed by implanting or diffusing phosphorus ions P ⁺ on the other side of the straight waveguide (3). 10. The all-silicon waveguide photoelectric converter according to claim 8 or 9, characterized in that the SOI substrate is composed of Si substrate (1), SiO ₂ lower cladding layer (2) arranged in sequence from bottom to top and Si thin layer (3). 11. The all-silicon waveguide photoelectric converter according to claim 9, characterized in that, the p-type doped region (4) and the n-type doped region (5) respectively have locally adopted metal Al or Al alloy electrodes prepared by evaporation method (6, 7). 12. The all-silicon waveguide photoelectric converter according to claim 8, characterized in that the curved waveguide (8) is tangent to the straight waveguide, the outer port of the curved waveguide (8) is the light wave incident end, and the light wave passes through the curved waveguide (8) incorporated into the straight waveguide resonant cavity (3). 13. The all-silicon waveguide photoelectric converter according to claim 12, characterized in that the bending radius of the curved waveguide (8) is proportional to the intensity of the returning light wave signal. 14. The all-silicon waveguide photoelectric converter according to claim 8, characterized in that the distributed Bragg reflection grating has periodic bar-shaped grooves, so as to form high reflection for communication light waves. 15. The all-silicon waveguide photoelectric converter according to claim 8, characterized in that the cavity length of the resonant cavity (3) between the two reflective gratings satisfies an integer multiple of the communication wavelength. 16. The all-silicon waveguide photoelectric conversion device according to claim 14 or 15, characterized in that the wavelength of the communication light wave is in the 1.55 micron band.

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