Method for manufacturing a photodetector integrated with a dual absorption region

Abstract

This invention relates to the field of integrated chips and discloses a method for fabricating a photodetector with integrated dual absorption regions. The photodetector includes, from bottom to top, a substrate, a second active absorption region, an optical transmission waveguide region, and a first active absorption region. The first active absorption region contains, in a transverse direction, a first P++ doped region, a first P+ doped region, a first intrinsic I region, a first N+ doped region, and a first N++ doped region, with the first P++ doped region electrically connected to a first metal electrode. The second active absorption region contains, in a transverse direction, a second P++ doped region, a second P+ doped region, a second intrinsic I region, a second N+ doped region, and a second N++ doped region, with the second P++ doped region electrically connected to a second metal electrode. The first and second N++ doped regions are electrically connected through a metal via. This photodetector has two different light absorption regions, enabling it to detect high-power and multi-band optical signals, exhibiting high responsivity and a large photoelectric response bandwidth.

Description

[0001] Case Analysis

[0002] This invention is a divisional application filed on December 30, 2021, with application number 2021116477561 and titled "Photodetector with integrated dual absorption regions and its fabrication method". Technical Field

[0003] This invention relates to the field of integrated chips, and in particular to a method for fabricating a photodetector with integrated dual absorption regions. Background Technology

[0004] Optical-electric detectors are generally used to detect light or other electromagnetic energy. Currently, detectors have important practical applications in wired or wireless communication, sensing, surveillance, and national security. Specifically, in optoelectronic integrated chips, the optical-electric detector is one of the core chips in the receiver, converting high-speed optical data into electrical signals. Optical-electric detectors generally utilize the thermoelectric, photoelectric, and electroabsorption effects of materials to detect the intensity of light. In the optical communication band, the main material systems currently used are III-V group materials, germanium (Ge), and silicon (Si). Although detectors based on these material systems have achieved good performance and commercialization, they still have many shortcomings, such as a single optical response wavelength, large device size, complex fabrication processes, and high cost. Summary of the Invention

[0005] Purpose of the invention: To address the problems existing in the prior art, the present invention provides a method for fabricating a photodetector with integrated dual absorption regions. This photodetector has two different light absorption regions, enabling it to detect high-power and multi-band optical signals, exhibiting high responsivity and a large photoelectric response bandwidth.

[0006] Technical Solution: This invention provides a photodetector with integrated dual absorption regions, comprising a substrate, a second active absorption region, an optical transmission waveguide region, and a first active absorption region arranged sequentially from bottom to top; the first active absorption region includes a first P++ doped region, a first P+ doped region, an undoped first intrinsic I region, a first N+ doped region, and a first N++ doped region arranged sequentially in the horizontal direction, the first P++ doped region being electrically connected to a first metal electrode; the second active absorption region includes a second P++ doped region, a second P+ doped region, an undoped second intrinsic I region, a second N+ doped region, and a second N++ doped region arranged sequentially in the horizontal direction, the second P++ doped region being electrically connected to a second metal electrode; the first N++ doped region and the second N++ doped region are electrically connected through a metal via between them.

[0007] Furthermore, a groove structure is formed in the middle of the optical transmission waveguide region. The refractive index (mode effective refractive index) of an optical waveguide is generally determined by the intrinsic refractive index of the material and the structure of the waveguide. Generally speaking, adjusting the waveguide structure is a common and effective method, which helps to design the coupling efficiency between waveguides. For the groove structure in this application, the refractive index can be adjusted by changing parameters such as the depth and width of the groove, as well as the width and thickness of the external optical waveguide cross section. The advantage of this groove structure is that it increases the dimension of refractive index adjustment, and more adjustment parameters are available to achieve efficient optical coupling between the optical transmission waveguide region and the first and second optical absorption regions.

[0008] Preferably, the width w1 of the first intrinsic I region is 50~500 nm; and / or, the width w2 of the second intrinsic I region is 50~500 nm. The widths of the first and second intrinsic I regions affect the 3dB bandwidth and detection quantum efficiency of the detector. Excessive width leads to a decrease in 3dB bandwidth, while excessive narrowness leads to a decrease in detection quantum efficiency. Controlling their widths within 50~500 nm achieves suitable 3dB bandwidth and detection quantum efficiency. Preferred values ​​are 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm, but are not limited to these listed values; other unlisted values ​​within this range are also applicable.

[0009] Furthermore, a portion of the first P+ doped region, the first intrinsic I region, and a portion of the first N+ doped region form a first optical absorption region; a portion of the second P+ doped region, the second intrinsic I region, and a portion of the second N+ doped region form a second optical absorption region; the optical transmission waveguide region is located between the first optical absorption region and the second optical absorption region.

[0010] Preferably, the distance h1 between the optical transmission waveguide region and the first optical absorption region is 50~400nm; and / or, the distance h2 between the optical transmission waveguide region and the second optical absorption region is 50~400nm. The distance between the optical transmission waveguide region and the first and second optical absorption regions affects the detector's detection efficiency and optical power detection range. If the distance is too large, less energy will be coupled into the absorption region, reducing the detection efficiency. If the distance is too small, the optical absorption region will easily saturate under high power incident light, resulting in a smaller detection optical power range. Controlling the distance between the two within 50~400nm helps to achieve high efficiency and high optical power detection. Preferably, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, etc., but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0011] Preferably, the doping concentrations of the first P++ doped region, the second P++ doped region, the first N++ doped region, and the second N++ doped region are all 1×10⁻⁶. 20 / cm 3 ~8×10 20 / cm 3 ; and / or, the doping concentrations of the first P+ doped region, the second P+ doped region, the first N+ doped region, and the second N+ doped region are each 1×10⁻⁶. 18 / cm 3 ~6×10 18 / cm 3 .

[0012] Preferably, the first intrinsic I region and the second intrinsic I region are optically absorbing materials with different optical absorption bands. Different materials correspond to different optical absorption ranges, which is determined by the material's band structure. For example, typical silicon optical absorption waveguides can only absorb light up to 1.1 μm and below; for light greater than 1.1 μm, silicon generally does not absorb it or has very low absorption efficiency. Germanium, on the other hand, can absorb light with wavelengths of 1.6 μm and below. However, compared to silicon, germanium has lower absorption efficiency below 1 μm, so light below 1 μm is preferentially detected and absorbed by silicon; light above 1 μm is preferentially detected and absorbed by germanium. The configuration of different absorption bands in the first and second optical absorption regions in this application enables the detection of broadband optical signals.

[0013] Preferably, the first intrinsic region I is any one of the following light-absorbing materials: germanium, germanium-silicon alloy, group III-V material or group III-V material alloy; and / or, the second intrinsic region I is any one of the following light-absorbing materials: silicon or perovskite.

[0014] Preferably, the substrate is silicon-on-insulator (SOI), which is formed by depositing silicon dioxide on a silicon substrate; and / or, the material of the optical transmission waveguide region is silicon nitride, aluminum nitride, or lithium niobate.

[0015] The present invention also provides a method for fabricating a photodetector with integrated dual absorption regions, the method being as follows: (1) depositing an insulating layer on a substrate to form a substrate, and depositing a second active absorption region thin film on the insulating layer of the substrate, and forming a ridge germanium waveguide structure after photolithography and etching; (2) sequentially performing P++ doping, N++ doping, P+ doping, and N+ doping on the ridge germanium waveguide structure to form a second P++ doped region, a second N++ doped region, a second P+ doped region, and a second N+ doped region, respectively, and retaining an undoped second intrinsic I region to form a second active absorption region; (3) depositing an insulating layer and planarizing it, and after photolithography to open a window, depositing a light transmission layer at an appropriate position. (3) Deposit waveguide material to form optical transmission waveguide region; (4) Deposit insulating layer, photolithography and etching followed by deposition of metal via material to form metal via; (5) Deposit first active absorption region material, photolithography and etching followed by formation of ridge silicon waveguide structure; (6) Perform P++ doping, N++ doping, P+ doping and N+ doping on ridge silicon waveguide structure in sequence to form first P++ doped region, first N++ doped region, first P+ doped region and first N+ doped region respectively, and retain the undoped first intrinsic I region to form first active absorption region; (7) Photolithography to open window, deposit first metal electrode and second metal electrode on first P++ doped region and second P++ doped region respectively.

[0016] Beneficial effects: In the photodetector with integrated dual absorption regions of the present invention, light passes through the optical transmission waveguide region and is coupled to the first and second optical absorption regions respectively. Thanks to the configuration of different absorption bands in the first and second optical absorption regions, broadband optical signals can be detected. Since the active region structure of the first and second optical absorption regions is PNNP, and a bias voltage is applied between the two P through the first and second metal electrodes, photogenerated carriers are extracted to generate electrical signals.

[0017] This photodetector allows the first and second light absorption regions to operate independently by adjusting the polarity of the bias voltage (see attached diagram in the abstract for details on the working principle), thus enabling integrability. The working principle is as follows:

[0018] This photodetector is a structure consisting of two PIN and NIP terminals connected in series via an N-connector. When a voltage is applied between the two P terminals, one PN junction will operate in forward bias and the other in reverse bias (basic principle of PN junctions). The detector must operate in reverse bias to extract photogenerated carriers and achieve signal detection. For example, when the incident light wavelength is λ1, coupling to the first absorption region requires the first PIN junction to operate in reverse bias, so the second PIN junction will operate in forward bias (detection will not be possible). When the incident light wavelength is λ2, coupling to the second absorption region requires the second PIN junction to operate in reverse bias (this can be achieved by adjusting the voltage V). BIf the first and second pins are reverse biased, then the first pin will be forward biased (detection will not be possible); to achieve reverse bias for the first and second pins respectively, it is only necessary to adjust the voltage difference applied between the two P-type pins. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the photodetector with integrated dual absorption regions in this invention;

[0020] Figure 2 This is a schematic diagram illustrating the working principle of a photodetector with integrated dual absorption regions. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] This embodiment provides a photodetector with integrated dual absorption regions, including a substrate 1, a second active absorption region, an optical transmission waveguide region 2, and a first active absorption region arranged sequentially from bottom to top.

[0023] The aforementioned substrate 1 is a silicon-on-insulator (SOI) formed by depositing silicon dioxide 102 on a silicon substrate 101;

[0024] The aforementioned second active absorption region includes a second P++ doped region 9, a second P+ doped region 10, an undoped second intrinsic I region 11, a second N+ doped region 12, and a second N++ doped region 13 arranged laterally in sequence. The second P++ doped region 9 is electrically connected to the second metal electrode 14. A portion of the second P+ doped region 10, the second intrinsic I region 11, and a portion of the second N+ doped region 12 form the second light absorption region.

[0025] The doping concentration of the second P++ doped region 9 and the second N++ doped region 13 is 1×10⁻⁶. 20 / cm 3 ~8×10 20 / cm 3 The doping concentration of both the second P+ doped region 10 and the second N+ doped region 12 is 1×10⁻⁶. 18 / cm 3 ~6×10 18 / cm 3 The second intrinsic region I, 11, is made of silicon, with a width w2 of 50~500nm.

[0026] The material of the aforementioned optical transmission waveguide region 2 is silicon nitride. In order to achieve efficient optical coupling between the optical transmission waveguide region 2 and the first and second optical absorption regions, the optical transmission waveguide region 2 in this embodiment is also provided with a groove structure that can adjust the refractive index.

[0027] The aforementioned first active absorption region includes a first P++ doped region 3, a first P+ doped region 4, an undoped first intrinsic I region 5, a first N+ doped region 6, and a first N++ doped region 7 arranged laterally in sequence. The first P++ doped region 3 is electrically connected to the first metal electrode 8. A portion of the first P+ doped region 4, the first intrinsic I region 5, and a portion of the first N+ doped region 6 form the first light absorption region.

[0028] The doping concentration of both the first P++ doped region 3 and the first N++ doped region 7 is 1×10⁻⁶. 20 / cm 3 ~8×10 20 / cm 3 The doping concentration of both the first P+ doped region 4 and the first N+ doped region 6 is 1×10⁻⁶. 18 / cm 3 ~6×10 18 / cm 3 The first intrinsic region I, region 5, is made of germanium, with a width w2 of 50~500 nm.

[0029] The first N++ doped region 7 and the second N++ doped region 13 are electrically connected through a metal via 15 between them.

[0030] The distance h1 between the optical transmission waveguide region 2 and the first optical absorption region is 50~400nm; the distance h2 between the waveguide region 2 and the second optical absorption region is 50~400nm.

[0031] The working principle of the above-mentioned photodetector with integrated dual absorption regions is as follows: Figure 2 As shown:

[0032] This photodetector consists of two PIN and NIP terminals connected in series via an N-connector. When a voltage is applied between the two P terminals, one PN junction will operate in forward bias and the other in reverse bias (basic principle of PN junctions). The detector must operate in reverse bias to extract photogenerated carriers and achieve signal detection. For example, when the incident light wavelength is λ1, it is coupled to the first absorption region, requiring the first PIN junction to operate in reverse bias, so the second PIN junction will operate in forward bias (detection will not be possible). When the incident light wavelength is λ2, it is coupled to the second absorption region, requiring the second PIN junction to operate in reverse bias, so the first PIN junction will operate in forward bias (detection will not be possible). To achieve reverse bias operation for the first and second PIN junctions respectively, it is only necessary to adjust the voltage difference applied between the two P terminals.

[0033] The fabrication method of the above-mentioned photodetector integrating dual absorption regions is as follows:

[0034] (1) A high-quality germanium thin film, namely the second active absorption region film, is prepared on a silicon-on-insulator (SOI) substrate 1 by plasma-enhanced chemical vapor deposition (PECVD); the deposited germanium thin film area is photolithographically etched to achieve pattern transfer and then etched to form a ridge-type germanium waveguide structure.

[0035] (2) The ridge-type germanium waveguide structure is sequentially doped with P++, N++, P+ and N+ to form the second P++ doped region 9, the second N++ doped region 13, the second P+ doped region 10 and the second N+ doped region 12 respectively, and the undoped germanium intrinsic region, namely the second intrinsic I region 11, is retained to form the second active absorption region.

[0036] (3) Deposit a silicon dioxide material layer and use chemical mechanical polishing technology to achieve planarization; open a window by photolithography, and use low pressure chemical vapor deposition (LPCVD) to prepare a silicon nitride thin film material at an appropriate position, and etch a groove structure on the silicon nitride thin film material to form an optical transmission waveguide region 2;

[0037] (4) Deposit a silicon dioxide material layer; after photolithography and etching, deposit a metal via material to form a metal via 15;

[0038] (5) Polycrystalline silicon material, i.e., the first absorption active region material, is prepared by plasma-enhanced chemical vapor deposition (PECVD); the deposited polycrystalline silicon region is photolithographically etched to achieve pattern transfer and then etched to form a ridge silicon waveguide structure;

[0039] (6) The ridge silicon waveguide structure is sequentially doped with P++, N++, P+ and N+ to form the first P++ doped region 3, the first N++ doped region 7, the first P+ doped region 4 and the first N+ doped region 6 respectively, and the undoped silicon intrinsic region structure, namely the first intrinsic I region 5, is retained to form the first active absorption region.

[0040] (7) Photolithography opens windows and deposits metal materials on the first P++ doped region 3 and the second P++ doped region 9 respectively to form the first metal electrode 8 and the second metal electrode 14.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for fabricating a photodetector integrating dual absorption regions, characterized in that, The preparation method is as follows: (1) An insulating layer is deposited on a substrate to form a substrate (1), and a second active absorption region thin film is deposited on the insulating layer of the substrate (1). After photolithography and etching, a ridge waveguide structure is formed. (2) The ridge waveguide structure is sequentially doped with P++, N++, P+ and N+ to form the second P++ doped region (9), the second N++ doped region (13), the second P+ doped region (10) and the second N+ doped region (12), respectively, and the undoped second intrinsic I region (11) is retained to form the second active absorption region; (3) Deposit an insulating layer and planarize it. After photolithography to open the window, deposit the optical transmission waveguide material at the appropriate position to form the optical transmission waveguide region (2). (4) Deposit an insulating layer, and deposit a metal through-hole material after photolithography and etching to form a metal through-hole (15). (5) Deposit the first absorbing active region material, and form a ridge waveguide structure after photolithography and etching; (6) The ridge waveguide structure is sequentially doped with P++, N++, P+ and N+ to form the first P++ doped region (3), the first N++ doped region (7), the first P+ doped region (4) and the first N+ doped region (6), respectively, and the first intrinsic I region (5) is retained without doping, forming the first active absorption region; (7) A window is opened by photolithography, and a first metal electrode (8) and a second metal electrode (14) are deposited on the first P++ doped region (3) and the second P++ doped region (9), respectively.

2. The method for fabricating a photodetector with integrated dual absorption regions according to claim 1, characterized in that, The photodetector comprises, from bottom to top, a substrate (1), a second active absorption region, an optical transmission waveguide region (2), and a first active absorption region; The first absorption active region includes a first P++ doped region (3), a first P+ doped region (4), an undoped first intrinsic I region (5), a first N+ doped region (6), and a first N++ doped region (7) arranged laterally in sequence. The first P++ doped region (3) is electrically connected to the first metal electrode (8). The second absorption active region includes a second P++ doped region (9), a second P+ doped region (10), an undoped second intrinsic I region (11), a second N+ doped region (12), and a second N++ doped region (13) arranged laterally in sequence. The second P++ doped region (9) is electrically connected to the second metal electrode (14). The first N++ doped region (7) and the second N++ doped region (13) are electrically connected through a metal via (15) between them.

3. The method for fabricating a photodetector with integrated dual absorption regions according to claim 2, characterized in that, The optical transmission waveguide region (2) has a groove structure in the middle.

4. The method for fabricating a photodetector with integrated dual absorption regions according to claim 2, characterized in that, The width w1 of the first intrinsic I region (5) is 50~500nm; And / or, the width w2 of the second intrinsic I region (11) is 50~500nm.

5. The method for fabricating a photodetector integrating dual absorption regions according to claim 2, characterized in that, A portion of the first P+ doped region (4), the first intrinsic I region (5), and a portion of the first N+ doped region (6) form a first optical absorption region; a portion of the second P+ doped region (10), the second intrinsic I region (11), and a portion of the second N+ doped region (12) form a second optical absorption region; the optical transmission waveguide region (2) is located between the first optical absorption region and the second optical absorption region.

6. The method for fabricating a photodetector with integrated dual absorption regions according to claim 5, characterized in that, The distance h1 between the optical transmission waveguide region (2) and the first optical absorption region is 50~400nm; And / or, the distance h2 between the optical transmission waveguide region (2) and the second optical absorption region is 50~400nm.

7. The method for fabricating a photodetector with integrated dual absorption regions according to claim 2, characterized in that, The doping concentrations of the first P++ doped region (3), the second P++ doped region (9), the first N++ doped region (7), and the second N++ doped region (13) are 1×10⁻⁶. 20 / cm 3 ~8×10 20 / cm 3 ; And / or, the doping concentrations of the first P+ doped region (4), the second P+ doped region (10), the first N+ doped region (6), and the second N+ doped region (12) are 1×10⁻⁶. 18 / cm 3 ~6×10 18 / cm 3 .

8. The method for fabricating a photodetector integrating a dual absorption region according to any one of claims 1 to 7, characterized in that, The first intrinsic region I (5) and the second intrinsic region I (11) are light-absorbing materials with different light absorption bands.

9. The method for fabricating a photodetector with integrated dual absorption regions according to claim 8, characterized in that, The first intrinsic region I (5) is any of the following light-absorbing materials: germanium, germanium-silicon alloy, group III-V material or group III-V material alloy; And / or, the second intrinsic region I (11) is any of the following light-absorbing materials: silicon or perovskite.

10. The method for fabricating a photodetector integrating a dual absorption region according to any one of claims 1 to 7, characterized in that, The substrate (1) is silicon-on-insulator (SOI), which is formed by depositing silicon dioxide (102) on a silicon substrate (101); And / or, the material of the optical transmission waveguide region (2) is silicon nitride, aluminum nitride or lithium niobate.

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