JP5150216B2 - Waveguide-type photodetector and manufacturing method thereof - Google Patents

Description

  The present invention relates to a waveguide type photodetector and a method for manufacturing the same.

  Along with the recent high integration of LSIs, the miniaturization of circuits inside the LSIs is progressing. With this miniaturization, the wiring cross-sectional area is reduced and the distance between adjacent wirings is reduced. Therefore, the wiring resistance inside the LSI increases and the capacitance between the wirings increases. As a result, the wiring delay time determined by the wiring resistance and the wiring capacitance increases, and it is difficult to further increase the speed of the LSI.

  Optical wiring technology has attracted attention as a technology for solving the wiring delay problem associated with high integration of LSIs. Optical wiring technology is a method of transmitting optical signals using optical waveguides, and does not increase the wiring resistance and inter-wiring capacitance due to the miniaturization as described above, and can be expected to further increase the operation speed. . An opto-electric hybrid LSI has been proposed as an LSI that performs signal transmission using such an optical wiring.

  An opto-electric hybrid LSI is an LSI using a method in which signal processing by each functional block is performed electrically, and an optical signal is transmitted between these functional blocks. Such an opto-electric hybrid LSI requires an element that converts an optical signal to be transmitted into an electric signal and an element that converts an electric signal subjected to signal processing into an optical signal.

  As an element for converting an electric signal into an optical signal, an edge-emitting laser or a surface-emitting laser (VCSEL) is used, and there is a report example of an operation in the GHz band.

  On the other hand, there are many reported examples of a light detection device used as an element for converting an optical signal into an electrical signal. In this apparatus, when light having energy larger than the band gap energy of the light absorption region is incident on the light absorption region, electron-hole pairs are generated, and each of these electrodes is generated by an internal electric field and an externally applied electric field. It is detected as a photocurrent.

  Such a light detection device includes a surface-type light detection device in which an optical waveguide is disposed outside the light-receiving element, and a waveguide-type light detection device in which the light-receiving element and the optical waveguide are integrated. However, at present, the development of a waveguide type photodetector is the mainstream because of the ease of design and creation for achieving high light receiving sensitivity while maintaining high speed.

  Currently known waveguide-type photodetectors are basically classified into the following two structures. That is, a structure in which a light absorption region is disposed above or below the optical waveguide, and electrodes are disposed above and below the light absorption region via a p-type semiconductor layer or an n-type semiconductor layer (hereinafter referred to as a vertical structure). And an optical waveguide formed on the semiconductor substrate is surrounded by a light absorption region, and electrodes are disposed on both side surfaces of the light absorption region via a p-type semiconductor layer or an n-type semiconductor layer, respectively ( (Hereinafter referred to as a horizontal structure).

  In the photodetection device having a vertical structure, the electrode is disposed above and below the light absorption region and the optical waveguide (Patent Document 1), and the electrode is disposed above and below the light absorption region disposed on the optical waveguide ( Patent document 2) is known. However, in order to operate the photodetector having the vertical structure described in Patent Document 1, it is necessary to generate an electric field also in the optical waveguide layer. For this reason, it is necessary to dope impurities into the optical waveguide to make the optical waveguide a conductive band. However, such impurities cause light scattering and light loss occurs in the optical waveguide inside the photodetecting device, resulting in a problem that conversion efficiency decreases. On the other hand, when operating the photodetector having a vertical structure described in Patent Document 2, the above problem is solved because it is not necessary to generate an electric field in the optical waveguide, but the n-type semiconductor layer or Since the light absorption region is disposed through the p-type semiconductor layer, a certain length of waveguide length is required until the light energy moves from the optical waveguide to the light absorption region, and there is a problem that the apparatus becomes large. Furthermore, since light energy passes from the optical waveguide to the light absorption region and passes through the n-type semiconductor layer or the p-type semiconductor layer, there is also a problem that light loss occurs in this portion and conversion efficiency is lowered.

Further, in the photodetection device having a horizontal structure, a light absorption region is formed so as to cover the periphery of the optical waveguide, and electrodes are arranged on both side surfaces thereof. There is a problem that it occurs to avoid the waveguide. For this reason, as shown below, several problems arise. First, since it takes a long time for electrons and holes generated in the light absorption region to reach each electrode, high-speed operation is limited. Second, the probability that electrons and holes recombine with majority carriers in the middle of drifting to each electrode increases, and conversion efficiency decreases. Third, the voltage required to operate this photodetection device increases, and the power consumption increases. Fourth, in order to optimize the operation speed of the photodetecting device, the arrangement accuracy of the p-type semiconductor layer and the n-type semiconductor layer formed on both sides of the light absorption region is important. Since it is limited to the pattern creation accuracy at the time of element creation, highly accurate alignment is required. (Patent Document 3)
JP 2006-171157 A JP-A-9-139520 JP-T-2006-522465

  An object of the present invention is to provide a photodetector that can operate at high speed with low power consumption.

The photodetector according to the present invention includes an optical waveguide made of a non-doped layer formed on a semiconductor substrate, a light absorption region formed so as to surround the optical waveguide, and a first portion formed above the light absorption region. An electrode and a second electrode formed on the lower or both sides of the light absorption region are provided.

  In the light detection device according to the present invention, the first conductive semiconductor layer formed in contact with the first electrode in the upper portion of the light absorption region, and the first conductive semiconductor layer in the lower portion or both sides of the light absorption region. And a second conductivity type semiconductor layer formed in contact with the two electrodes.

  Furthermore, in the photodetecting device according to the present invention, the second electrode formed in the lower part of the light absorption region is outside the light absorption region and at a position in front of or behind the light propagation direction. It is formed on a semiconductor substrate.

  Furthermore, in the photodetector according to the present invention, the light absorption region is an intrinsic semiconductor region, or includes a first conductivity type semiconductor layer and a second conductivity type semiconductor layer bonded to the first conductivity type semiconductor layer. It is what.

  Furthermore, in the photodetection device according to the present invention, when the conductivity type of the first conductivity type semiconductor layer is p type, the conductivity type of the second conductivity type semiconductor layer is n type, or the first conductivity type semiconductor When the conductivity type of the layer is n-type, the conductivity type of the second conductivity type semiconductor layer is p-type.

  Furthermore, in the photodetector according to the present invention, an optical waveguide layer is formed on both sides of the bottom of the optical waveguide, and the thickness of the optical waveguide layer is 30 nm or less.

  Furthermore, in the photodetector according to the present invention, the semiconductor forming the light absorption region is any one of Ge, Si, SiGe, InGaAs, InGaAsP, GaSb, InGaSb, GaAsSb, and InGaAsSb, and the optical waveguide and the optical waveguide The material of the waveguide layer is any one of Si, SiN, SiON, SiOC, and SiCN.

  Furthermore, in the photodetecting device according to the present invention, an electric field is applied in the reverse direction from the outside between the first electrode and the second electrode.

Further, in the method for manufacturing a photodetector according to the present invention, a step of forming an optical waveguide made of a non-doped layer on a semiconductor substrate, a step of forming a light absorption region so as to surround the optical waveguide, Forming a first conductive type semiconductor layer on the upper part; forming a first electrode on the first conductive type semiconductor layer; and forming a second conductive type semiconductor layer on both sides or under the light absorption region. And a step of forming a second electrode on the second conductivity type semiconductor layer.

  Furthermore, in the method for manufacturing a photodetector according to the present invention, the step of forming the optical waveguide includes a step of etching so as to extend and form an optical waveguide layer having a thickness of 30 nm or less on both sides of the bottom of the optical waveguide. It is characterized by including.

  According to the present invention, since the electrodes are arranged on the upper and lower portions of the light absorption region, or on the upper and both sides, the internal electric field can be generated at the shortest distance so as to avoid the optical waveguide. For this reason, the photodetector which can operate at high speed with low power consumption is obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

(Embodiment 1)
FIG. 1 is a view showing an embodiment of the present invention, FIG. 1A is a top view, and FIG. 1B is a cross-sectional view taken along a broken line AA ′ shown in FIG.

As shown in FIG. 1, in the photodetector of the first embodiment, a clad layer 12 is formed on a semiconductor substrate 11, and an optical waveguide 14 is formed on the clad layer 12. An optical waveguide layer 13 is formed on both sides of the bottom of the optical waveguide 14, and an optical absorption region is formed on the optical waveguide layer 13 and the optical waveguide 14 with an intrinsic semiconductor so as to cover both sides and the upper surface of the optical waveguide 14. 15 is formed. An n-type semiconductor layer 16 is formed on the light absorption region 15, and a p-type semiconductor layer 17 is formed on both sides. That is, the light absorption region 15, the n-type semiconductor layer 16, and the p-type semiconductor layer 17 form a pin structure. Electrodes 18 and 19 are formed in contact with the n-type semiconductor layer 16 and the p-type semiconductor layer 17, respectively. Also, of the upper portion of the p-type semiconductor layer 17, the portion where the electrode 19 is not formed in contact is covered with SiO ₂ insulator masks 20, further out electrode 18 of the upper part of the SiO ₂ insulator masks 20 and the light absorbing region 15 The part other than the part formed in contact is covered with an insulating film 21.

  When an optical signal propagates through the optical waveguide 14 from a direction perpendicular to the paper surface of this apparatus, light absorption occurs in the light absorption region 15 formed so as to surround the optical waveguide 14. When the optical signal is absorbed by the light absorption region 15, a hole-electron pair is generated inside. Here, when a voltage is applied so that the electrode 18 is positive and the electrode 19 is negative, when these holes and electrons are generated on the left side of the optical waveguide 14, the p-type semiconductor layer 17 and the n-type semiconductor layer on the left side. 16 drifts due to the electric field generated between the two and is detected as a current. Further, if it occurs on the right side of the optical waveguide 14, it drifts due to the electric field generated between the right p-type semiconductor layer 17 and the n-type semiconductor layer 16 and is detected as a current. Here, since the pin structure is formed in an oblique direction on a plane perpendicular to the light propagation direction, it is possible to perform light detection that avoids the disadvantages of the conventional vertical structure and horizontal structure. That is, it is not necessary to generate an electric field in the optical waveguide 14 as compared with a photodetection device having a vertical structure, so that it is not necessary to dope the optical waveguide 14 with impurities, and optical signal loss can be reduced. Further, since the optical waveguide 14 and the light absorption region 15 are joined, the waveguide length necessary for absorbing the optical signal can be shortened, and the apparatus can be reduced in size and power consumption. In addition, the distance between the electrodes 18 and 19 can be shortened and an electric field can be applied so as to avoid the optical waveguide 14 as compared with the light detection device having a horizontal structure, so that high speed and low power consumption can be realized. Since the recombination probability between the hole-electron pair generated in the light absorption region 15 and the majority carrier can be lowered, the conversion efficiency can be improved. Furthermore, since the p-type semiconductor layer 17 and the n-type semiconductor layer 16 are not arranged in the same manner as the lateral structure, the alignment accuracy is relaxed.

  Next, a manufacturing process of the waveguide type photodetector shown in FIG. 1 which is an embodiment of the present invention will be described with reference to FIGS. 2A to 2D (a) to (l). 2A to 2D are cross-sectional views taken along the broken line A-A ′ of the waveguide type photodetector shown in FIG.

  In this embodiment, as shown in FIG. 2A (a), when a Si substrate is used as the semiconductor substrate 11, a buried oxide film layer is used as the cladding layer 12, and an SOI substrate in which the Si layer has a laminated structure is used as the optical waveguide layer 13. The manufacturing process is shown.

  First, as shown in FIG. 2A (b), a conductive region forming mask 22 is formed on the optical waveguide layer 13.

  Next, as shown in FIG. 2A (c), a p-type semiconductor layer 17 is formed by ion implantation or thermal diffusion.

Next, as shown in FIG. 2B (d), after removing the conductive region forming mask 22, a SiO ₂ insulator mask 20 is formed to form the optical waveguide 14.

  Next, as shown in FIG. 2B (e), the optical waveguide layer 13 is etched using dry etching to form the optical waveguide 14. At this time, in order to use the portion etched in the step shown in FIG. 2C (g) as the base of region selective crystal growth, the optical waveguide layer 13 of 30 nm or less is left above the boundary between the cladding layer 12 and the optical waveguide layer 13. Etch.

Next, as shown in FIG. 2B (f), only the SiO ₂ insulator mask 20 formed on the optical waveguide 14 is removed.

Next, as shown in FIG. 2C (g), a light absorption region 15 is formed around the optical waveguide 14 by crystal growth. At this time, no crystal is grown on the SiO ₂ insulator mask 20, and the light absorption region 15 is formed with the optical waveguide layer 13 left thin as a base. The light absorption region 15 is formed of an intrinsic semiconductor having a band gap energy equal to or less than the energy of incident light, and is formed of, for example, Ge, Si, SiGe, InGaAs, InGaAsP, GaSb, InGaSb, GaAsSb, or InGaAsSb. Is done.

  Next, as shown in FIG. 2C (h), an insulating film 21 is deposited on the entire surface of the element.

  Next, as shown in FIG. 2C (i), a part of the upper portion of the light absorption region 15 in the deposited insulating film 21 is removed by etching to form a window structure 23 for forming the electrode 18. .

  Next, as shown in FIG. 2D (j), the n-type semiconductor layer 16 is formed using the insulating film 21 as a mask.

  Next, as shown in FIG. 2D (k), an electrode metal is deposited on the window structure 23 formed in FIG. 2C (i) to form an n-side electrode 18.

Next, as shown in FIG. 2D (l), the insulating film 21 and the SiO ₂ insulator mask 20 deposited on the p-type semiconductor layer 17 are partially removed to form an electrode 19. 24 is formed.

  Finally, electrode metal is vapor-deposited on the window structure 24 formed in FIG. 2D (l) to form the p-side electrode 19 to complete the waveguide type photodetection device shown in FIG.

(Embodiment 2)
FIG. 3 is a view showing another embodiment of the present invention, where FIG. 3A is a top view, and FIG. 3B is a cross-sectional view taken along the broken line AA ′ shown in FIG. .

  As shown in FIG. 3, the photodetector of the second embodiment is characterized in that the p-type semiconductor layer 17 is formed on the cladding layer 12 and on the left and right of the optical waveguide 14. Even with such a structure, the disadvantages of the conventional vertical structure and horizontal structure can be avoided as in the structure shown in the first embodiment. In addition, the structure shown in FIG. 3 can determine the travel distance of the generated carrier by the thickness of the light absorption region 15, and a waveguide type photodetector that can operate at a higher speed by reducing this thickness. Can be realized.

  In addition, the manufacturing process of the waveguide type photodetector shown in Embodiment 2 can be realized by changing part of the manufacturing process shown in FIGS. 2A to 2D as appropriate.

(Embodiment 3)
FIG. 4 is a view showing another embodiment of the present invention, where FIG. 4A is a top view, and FIG. 4B is a cross-sectional view taken along the broken line AA ′ shown in FIG. .

  As shown in FIG. 4, the photodetector of the third embodiment includes an n-type semiconductor layer 16 in a part of the upper part of the light absorption region 15, and a p-type semiconductor in a part of both sides of the light absorption region 15. A layer 17 is included. Since this structure is formed by selectively doping the p-type semiconductor layer 17 and the n-type semiconductor layer 16 in the light absorption region 15 formed by selective growth, the non-doped region where the generated carriers existing between these layers travel. Therefore, a waveguide type photo-detecting device capable of a higher speed response can be realized.

  The technical characteristics of the manufacturing process of the waveguide type photodetector shown in Embodiment 3 are the same as the manufacturing process shown in FIGS. 2A to 2D. The waveguide type photodetection device shown in the embodiment can be realized.

(Embodiment 4)
FIG. 5 is a view showing another embodiment of the present invention, wherein FIG. 5A is a top view, and FIG. 5B is a cross-sectional view taken along a broken line AA ′ shown in FIG. (C) is sectional drawing along broken line BB 'shown to the figure (a).

  As shown in FIG. 5, in the photodetecting device according to the fourth embodiment, the electrode 19 formed in contact with the p-type semiconductor layer 17 is positioned outside the light absorption region 15 and forward or backward with respect to the light traveling direction. It is characterized by being formed.

  In this structure as well as in FIG. 3, the travel distance of the generated carriers can be determined by the thickness of the light absorption region 15, and by reducing the film thickness, a photodetector capable of high-speed operation can be realized. . In the step of forming the light absorption region 15 by selectively growing the crystal around the optical waveguide 14, the doped p-type semiconductor layer 17 is crystal-grown under the light absorption region 15, and the light absorption region is formed thereon. 15 is formed by crystal growth, it is not necessary to form the impurity semiconductor layer and the light absorption region 15 in separate steps, and the manufacturing process can be simplified. In other manufacturing processes, the waveguide-type photodetector shown in the present embodiment can be realized by changing part of the manufacturing processes shown in FIGS. 2A to 2D as appropriate.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to these.

  For example, in each of the above-described embodiments, the n-type semiconductor layer 16 and the p-type semiconductor layer 17 may be an n + -type semiconductor layer and a p + -type semiconductor layer having higher impurity concentrations than these, respectively, and have the same conductivity but different impurity concentrations. The conductive semiconductor layer may be a bonded semiconductor layer, or the p-type semiconductor layer 17 and the n-type semiconductor layer 16 may not be present. Further, the same effects can be obtained even if the semiconductor layers 16 and 17 and the semiconductor layer having a higher impurity concentration than those shown in FIG.

  In addition, the method for forming the p-type semiconductor layer 17 and the n-type semiconductor layer 16 and the method for forming an impurity semiconductor layer having an impurity concentration higher than these in each of the embodiments described above may be performed by selectively doping the light absorption region 15. When the optical waveguide layer 13 is selectively doped, the doped layer is selectively grown at a position adjacent to the light absorption region 15, or a combination of these is used. However, the same effect can be obtained.

  Further, in each of the above-described embodiments, the insulating film 21 is not necessarily required. Even without the insulating film 21, a process of selectively doping the upper portion of the light absorption region 15, a structure formed thereby, and a selective process If a structure in which the electrode can be formed in contact with the doped region and a structure in which the electrode is electrically insulated from other regions are applied, the same effect can be obtained.

  Further, the arrangement of the electrode 19 formed in contact with the p-type semiconductor layer 17 shown in the fourth embodiment can be applied to any of the above embodiments.

  As described above, the embodiment of the present invention can be implemented with various modifications without departing from the spirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a structural diagram which shows Embodiment 1 of this invention, the figure (a) is a top view, (b) is sectional drawing along the broken line A-A 'shown to the figure (a). It is sectional drawing which shows the manufacturing process of Embodiment 1 of this invention. It is sectional drawing which shows the manufacturing process of Embodiment 1 of this invention. It is sectional drawing which shows the manufacturing process of Embodiment 1 of this invention. It is sectional drawing which shows the manufacturing process of Embodiment 1 of this invention. FIG. 4 is a structural diagram showing Embodiment 2 of the present invention, where FIG. 4A is a top view, and FIG. 4B is a cross-sectional view taken along a broken line A-A ′ shown in FIG. FIG. 4 is a structural diagram showing Embodiment 3 of the present invention, where FIG. 4A is a top view, and FIG. 4B is a cross-sectional view taken along a broken line A-A ′ shown in FIG. FIG. 6 is a structural diagram showing Embodiment 4 of the present invention, where FIG. 5A is a top view, FIG. 5B is a cross-sectional view taken along a broken line AA ′ shown in FIG. ) Is a cross-sectional view along the broken line BB ′ shown in FIG.

Explanation of symbols

11: Semiconductor substrate 12: Clad layer 13: Optical waveguide layer 14: Optical waveguide 15: Light absorption region 16: N-type semiconductor layer 17: P-type semiconductor layer 18, 19: Electrode 20: SiO ₂ insulator mask 21: Insulating film 22: Conductive region forming masks 23, 24: Window structure

Claims (12)

An optical waveguide made of a non-doped layer formed on a semiconductor substrate, a light absorption region formed so as to surround the waveguide, a first electrode formed above the light absorption region, and the light absorption region And a second electrode formed on a lower part or both side parts.   A first conductive type semiconductor layer formed in contact with the first electrode in the upper part of the light absorption region, and a second conductivity formed in contact with the second electrode in the lower part or both sides of the light absorption region. The waveguide-type photodetector according to claim 1, further comprising a type semiconductor layer.   The second electrode formed under the light absorption region is formed on the semiconductor substrate outside the light absorption region and at a position in front of or behind the light propagation direction. The waveguide type photodetector according to claim 2.   The waveguide light detection device according to claim 2, wherein the light absorption region is an intrinsic semiconductor region.   3. The waveguide type photodetector according to claim 1, wherein the light absorption region includes a first conductivity type semiconductor layer and a second conductivity type semiconductor layer bonded to the first conductivity type semiconductor layer.   When the conductivity type of the first conductivity type semiconductor layer is p type, the conductivity type of the second conductivity type semiconductor layer is n type, or when the conductivity type of the first conductivity type semiconductor layer is n type, the first type 6. The waveguide type photodetector according to claim 2, wherein the conductivity type of the two-conductivity-type semiconductor layer is p-type.   7. A waveguide type photo detector according to claim 1, wherein an optical waveguide layer is extended on both sides of the bottom of the optical waveguide, and the thickness of the optical waveguide layer is 30 nm or less. .   8. The waveguide according to claim 1, wherein the semiconductor forming the light absorption region is any one of Ge, Si, SiGe, InGaAs, InGaAsP, GaSb, InGaSb, GaAsSb, and InGaAsSb. Type photodetection device.   9. The waveguide type photo detector according to claim 1, wherein the material of the optical waveguide and the optical waveguide layer is any one of Si, SiN, SiON, SiOC, and SiCN.   10. The waveguide type photodetector according to claim 1, wherein an electric field is applied between the first electrode and the second electrode in the reverse direction from the outside. A step of forming an optical waveguide composed of a non-doped layer on a semiconductor substrate, a step of forming a light absorption region so as to surround it, a step of forming a first conductivity type semiconductor layer above the light absorption region, Forming a first electrode on the first conductivity type semiconductor layer; forming a second conductivity type semiconductor layer on both sides or under the light absorption region; and forming a second electrode on the second conductivity type semiconductor layer. And a step of forming the electrode. A method for manufacturing a waveguide-type photodetector.   12. The waveguide according to claim 11, wherein the step of forming the optical waveguide includes an etching step so as to extend and form an optical waveguide layer having a thickness of 30 nm or less on both sides of the bottom of the optical waveguide. Method for manufacturing a mold photodetection device.

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