Semiconductor photodetector

Abstract

This semiconductor light-receiving element 10 comprises: a semiconductor laminate 20 that is formed on the upper surface of a semiconductor substrate 11 and is obtained by laminating in order a first semiconductor layer 21 having a first conductive type, a light absorption layer 22 composed of a semiconductor, and a second semiconductor layer 23 having a second conductive type; a first insulator layer 12 that is formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20; a first electrode 13 and a second electrode 14 which are formed on the upper surface of the first insulator layer 12; wiring 16 that connects the first electrode 13 and the second electrode 14, and the first semiconductor layer 21 and the second semiconductor layer 22; and a metal layer 15 which is formed on the upper surface of the first insulator layer 12 so as to cover the semiconductor laminate 20 and the wiring 16, and is electrically separated from the first electrode 13 and the second electrode 14.

Description

[Technical Field]

[0001] This disclosure relates to a semiconductor photodetector. [Background technology]

[0002] In response to the recent increase in communication traffic, there is a growing demand for faster and more sensitive optical receivers to improve the amount of data transmitted per unit of time, as well as for miniaturization of optical receivers to accommodate them at high density. In recent years, for single-channel optical receivers, optical receivers with shapes called TO-CAN and LC-ROSA have been widely used.

[0003] Photodiodes (PDs) are widely used as semiconductor light-receiving elements. A photodiode is a device that performs photoelectric exchange by generating electrons and holes when light with an energy greater than the semiconductor's band gap is irradiated onto it and the light is absorbed. The most basic type is called a pin photodiode (pin-PD). This consists of an i-layer with a low impurity density sandwiched between p-type and n-type semiconductors with high impurity density. When a reverse bias is applied to this pin structure, an electric field is generated in the i-layer, sweeping the electrons and holes generated by the light irradiation and generating a photocurrent.

[0004] In optical receivers, a differential voltage signal is required as input to the digital signal processor (DSP) located downstream of the photodiode; therefore, the photodiode cannot be directly connected to the digital signal processor. Typically, in optical receivers, a transimpedance amplifier (TIA) is connected between the photodiode and the digital signal processor to amplify the output current from the photodiode, convert it into a differential voltage signal, and then input it to the digital signal processor for signal processing.

[0005] In optical receivers of the TO-CAN and LC-ROSA types, which are widely used in optical communications, it is common to mount the photodiode and digital signal processor on the same plane (see Patent Document 1 and Non-Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-187607 [Non-patent literature]

[0007] [Non-Patent Document 1] T. Ohno, Y. Muramoto, K. Sano, S. Kodama, and N. Shigekawa, “A CAN-type MIC-PD ROSA operating at 40-Gbit / s” ECOC 2010, Th.10.D.2, Torino, Italy [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In the aforementioned type of optical receiver, light is incident perpendicularly to the plane on which the photodiode and transimpedance amplifier are mounted. While mounting the photodiode on top of the transimpedance amplifier in this type of optical receiver reduces the mounting area and meets the demand for further miniaturization, electromagnetic induction can cause inter-circuit interference between the transimpedance amplifier and the photodiode.

[0009] Circuit interference can be caused by electrostatic induction due to electric fields, electromagnetic induction due to magnetic fields, and induction via radio waves. Induction from the source circuit generates noise current in the receiving circuit, causing deterioration of the frequency characteristics and receiving sensitivity of the optical receiver. Since alternating current flows through any circuit, both the photodiode and the transimpedance amplifier can be both noise sources and receivers. However, the strength of the noise current due to induction increases in proportion to the current flowing through the source. Therefore, the noise current is greater when the transimpedance amplifier, through which amplified current flows, is the source. Note that inserting an insulating layer between the photodiode and the transimpedance amplifier has little effect in suppressing electrical interference.

[0010] This disclosure is proposed in view of the above-mentioned circumstances and aims to provide a semiconductor photodetector that enables space-saving in implementation without degrading reception sensitivity. [Means for solving the problem]

[0011] To solve the above-mentioned problems, the semiconductor photodetector of this disclosure includes a semiconductor laminate formed on the upper surface of a semiconductor substrate, in which a first semiconductor layer having a first conductivity type, a light-absorbing layer made of semiconductor, and a second semiconductor layer having a second conductivity type are sequentially stacked; a first insulating layer formed on the upper surface of the semiconductor substrate so as to cover the semiconductor laminate; a first electrode and a second electrode formed on the upper surface of the first insulating layer; wiring connecting the first electrode and the second electrode to the first semiconductor layer and the second semiconductor layer, respectively; and a metal layer formed on the upper surface of the first insulating layer so as to cover the semiconductor laminate and the wiring, which is electrically separated from the first electrode and the second electrode.

[0012] In addition, the semiconductor light-receiving element of the present disclosure includes a semiconductor laminate in which a first semiconductor layer having a first conductivity type, a light absorption layer made of semiconductor, and a second semiconductor layer having a second conductivity type are sequentially laminated on the upper surface of a semiconductor substrate, a first insulator layer formed to cover the lower surface of the semiconductor substrate, and a metal layer formed to cover the semiconductor laminate and the wiring connected to the semiconductor laminate on the lower surface of the first insulator layer.

Effects of the Invention

[0013] According to the present disclosure, it is possible to provide a semiconductor light-receiving element capable of realizing space saving in mounting without degrading the reception sensitivity.

Brief Description of the Drawings

[0014] [Figure 1] It is a cross-sectional view of the semiconductor light-receiving element of the first embodiment. [Figure 2] It is a top view of the semiconductor light-receiving element of the first embodiment. [Figure 3] It is a cross-sectional view showing a state where the semiconductor light-receiving element of the first embodiment is mounted on a transimpedance amplifier. [Figure 4] It is a top view of the semiconductor light-receiving element of the first modification of the first embodiment. [Figure 5] It is a cross-sectional view of the semiconductor light-receiving element of the second modification of the first embodiment. [Figure 6] It is a cross-sectional view of the semiconductor light-receiving element of the second embodiment. [Figure 7] It is a cross-sectional view showing a state where the semiconductor light-receiving element of the second embodiment is mounted on a transimpedance amplifier. [Figure 8] It is a cross-sectional view of the semiconductor light-receiving element of the first modification of the second embodiment. [Figure 9] It is a cross-sectional view showing the semiconductor light-receiving element of the second modification of the second embodiment. [Figure 10] It is a cross-sectional view showing a state where the semiconductor light-receiving element of the third embodiment is mounted on a transimpedance amplifier. [Figure 11]This is a cross-sectional view of a semiconductor photodetector, a modified example of the third embodiment. [Figure 12] This is a cross-sectional view of a semiconductor photodetector according to the fourth embodiment. [Figure 13] This is a cross-sectional view of a semiconductor photodetector, a modified example of the fourth embodiment. [Modes for carrying out the invention]

[0015] Hereinafter, the semiconductor photodetector of this embodiment will be described in order from the first embodiment to the fourth embodiment with reference to the drawings.

[0016] (First Embodiment) Figure 1 is a cross-sectional view showing a semiconductor photodetector 10 of the first embodiment. The semiconductor photodetector 10 of the first embodiment is a back-side incident type that receives incident light 102 incident from the back surface 101. The semiconductor photodetector 10 of the first embodiment includes a semiconductor substrate 11, a semiconductor laminate 20 formed by sequentially stacking a first semiconductor layer 21 having a first conductivity type, a light absorption layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type on the upper surface of the semiconductor substrate 11, and a first insulating layer 12 formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. The semiconductor laminate 20 constitutes a PIN photodiode.

[0017] In the semiconductor laminate 20, the light-absorbing layer 22 is composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 are composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to have their respective conductivity types by introducing impurities, and the light-absorbing layer 22 is in a state where the impurity concentration is lower than that of the first semiconductor layer 21 and the second semiconductor layer 23.

[0018] The semiconductor substrate 11 may be composed of semi-insulating InP. The first semiconductor layer 21 is an n-type impurity with a high concentration introduced. +-It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. + -It may be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23. The first insulator layer 12 may be composed of silicon oxide, silicon nitride, etc.

[0019] The semiconductor photodetector 10 further comprises a first electrode 13 and a second electrode 14 formed on the upper surface of a first insulator layer 12, wiring 16 connecting the first electrode 13 and the second electrode 14 to a first semiconductor electrode 24 and a second semiconductor electrode 25, respectively, and a metal layer 15 formed on the upper surface of the first insulator layer 12 so as to cover the semiconductor laminate 20 and the wiring 16, and electrically separated from the first electrode 13 and the second electrode 14. The first electrode 13 and the second electrode 14 have a cylindrical shape and extend to a predetermined depth from the upper surface of the first insulator layer 12. A first pad 13a and a second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14, respectively, to ensure a flat surface for connection. The first pad 13a and the second pad 14a may be plated. The first pad 13a and the second pad 14a are higher than the upper surface of the metal layer 15 and reach a predetermined height 103.

[0020] Figure 2 is a top view of a semiconductor photodetector 10 according to the first embodiment. A first pad 13a and a second pad 14a are formed on the upper surface of a first insulating layer 12 which has a substantially rectangular shape, near the approximate center of each of a pair of opposing sides. A metal layer 15 is formed on the upper surface of the first insulating layer 12, except for a substantially trapezoidal region where the longer side lies on the pair of opposing sides that surround the first pad 13a and the second pad 14a. The metal layer 15 is electrically separated from the first pad 13a and the second pad 14a, and from the first electrode 13 and the second electrode 14 connected to the first pad 13a and the second pad 14a, respectively, by the substantially trapezoidal region where the first insulating layer 12 is exposed. The metal layer 15 also covers the semiconductor laminate 20 and the wiring 16, providing electromagnetic shielding.

[0021] Here, we will explain the thickness of the first insulating layer 12. If the first insulating layer 12 between the wiring 16 and the metal layer 15 is thin, the current component that should flow to the transimpedance amplifier 50 may flow to the metal layer 15. Input impedance Z from wiring 16 to metal layer 15 in_m It can be represented by the number 1.

number

[0022] In equation 1, ω is the frequency of the current, ε is the permittivity of vacuum, ε0 is the permittivity of the material of the first insulating layer 12, S is the area of ​​the wiring 16, and d is the thickness of the first insulating layer 12. Input impedance Z to the transimpedance amplifier 50 in_TIA If we set Z to 50Ω, in_m If the impedance is 500Ω or more (more than 10 times), the amount of components that flow into the metal layer 15 can be reduced to less than 1 / 10. Therefore, ε0, S, and d are adjusted according to the required frequency band, and Z in_m By setting the resistance to 500Ω or more, a semiconductor photodetector 10 can be realized that suppresses current loss to the metal layer 15.

[0023] For example, ω = 25 GHz, ε = 2.7 (dielectric constant of benzocyclobutene, which is commonly used as an insulating material in semiconductor products), ε0 = 8.8 × 10⁻⁶ -12, when S = 2×10 -9 m and d = 1 μm, Z in_m = 842 Ω and satisfies the above conditions. That is, if the thickness of the first insulator layer 12 is 1 μm or more, current loss to the metal layer 15 can be sufficiently suppressed. Regarding the thickness of such a first insulator layer 12, the same applies to the semiconductor light-receiving element 10 of other embodiments.

[0024] A method for manufacturing the semiconductor light-receiving element 10 of the first embodiment will be described. The semiconductor laminate 20 deposited on the upper surface of the semiconductor substrate 11 is processed into a desired shape by wet etching or the like, and the first semiconductor electrode 24 and the second semiconductor electrode 25 are formed on the semiconductor laminate 20. A mirror or the like for reflecting the incident light 102 may be formed on the upper surface of the semiconductor laminate 20. Subsequently, a part of the first insulator layer 12 is formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. Further, after forming the first electrode 13, the second electrode 14, and the wiring 16 by plating, vapor deposition, or the like, the remaining portion of the first insulator layer 12 is formed on the upper part thereof. The first insulator layer 12 is removed from above the first electrode 13 and the second electrode 14 by dry etching or the like. Finally, the metal layer 15, the first pad 13a, and the second pad 14a are formed by plating, vapor deposition, or the like. The first pad 13a and the second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14 and are made higher than the upper surface of the metal layer 15.

[0025] FIG. 3 is a cross-sectional view showing a state where the semiconductor light-receiving element 10 of the first embodiment is mounted on the transimpedance amplifier 50. The semiconductor light-receiving element 10 of the first embodiment is a back-illuminated type that receives the incident light 102 from the back surface 101 and is flip-chip mounted on the upper surface of the transimpedance amplifier 50 so as to be able to receive the incident light 102 from above. The semiconductor light-receiving element 10 is inverted in the vertical direction so that its upper surface faces the upper surface of the transimpedance amplifier 50, and the first pad 13a and the second pad 14a are respectively connected to the input terminals 51 formed on the upper surface of the transimpedance amplifier 50. The connection between the first pad 13a and the second pad 14a and the input terminal 51 may be by soldering.

[0026] In the first embodiment, the semiconductor photodetector 10 has a metal layer 15 formed on the upper surface of the first insulating layer 12 that covers the semiconductor laminate 20 and wiring 16. Therefore, the semiconductor laminate 20 and wiring 16 of the semiconductor photodetector 10 are electrically shielded, preventing electromagnetic interference from the semiconductor laminate 20 and wiring 16 from reaching the transimpedance amplifier 50. As a result, the deterioration of receiving sensitivity caused by noise current due to interference is suppressed, and at the same time, it is possible to save space in the mounting area by flip-chip mounting the semiconductor photodetector 10 on the transimpedance amplifier 50.

[0027] Figure 4 is a top view of a first modified example of the semiconductor photodetector 10 of the first embodiment. In the first modified example, a third pad 31, a first pad 13a, and a second pad 14a are formed sequentially along one side of the substantially rectangular top surface. The third pad 31 does not have to be formed on the top surface of a columnar electrode like the first electrode 13 and the second electrode 14, as is the case with the first pad 13a and the second pad 14a, but may be formed on the top surface of the first insulating layer 12. The third pad 31 may also be connected to the first pad 13a or the second pad 14a. The top surface of the first insulating layer 12 has a metal layer 15 formed on it, except for substantially trapezoidal regions with a longer side on one side that surround the third pad 31, the first pad 13a, and the second pad 14a, respectively. The metal layer 15 is electrically isolated from the third pad 31, the first pad 13a, and the second pad 14a, as well as the first electrode 13 and the second electrode 14 connected to the first pad 13a and the second pad 14a, respectively, by the substantially trapezoidal region where the first insulating layer 12 is exposed. Furthermore, the metal layer 15 covers the semiconductor laminate 20 and the wiring 16, providing electromagnetic shielding.

[0028] Therefore, the semiconductor photodetector 10 of the first modified embodiment, like the semiconductor photodetector 10 of the first embodiment, suppresses the degradation of receiving sensitivity caused by noise current due to interference, while also achieving space saving in mounting area by flip-chip mounting the semiconductor photodetector 10 on the transimpedance amplifier 50. Furthermore, the semiconductor photodetector 10 of the first modified embodiment has a third pad 31 on the upper surface of the first insulating layer 12, and by securing the number of pads, the design of wiring and the like can be made easier. In addition to the third pad 31, the number of pads provided on the upper surface of the first insulating layer 12 may be further increased.

[0029] Figure 5 is a cross-sectional view showing a semiconductor photodetector 10 of a second modification of the first embodiment. The semiconductor photodetector 10 of the second modification is a surface-incident type that receives incident light 102 incident from above. The semiconductor photodetector 10 of the second modification has a semiconductor substrate 11 and a semiconductor laminate 20 in which a first semiconductor layer 21 having a first conductivity type, a light-absorbing layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type are sequentially stacked on the upper surface of the semiconductor substrate 11. The semiconductor laminate 20 constitutes a PIN photodiode.

[0030] In the semiconductor laminate 20, the light-absorbing layer 22 is composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 are composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to have their respective conductivity types by introducing impurities, and the light-absorbing layer 22 is in a state where the impurity concentration is lower than that of the first semiconductor layer 21 and the second semiconductor layer 23.

[0031] Even if the semiconductor substrate 11 is composed of semi-insulating InP, the first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. +-It may also be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23.

[0032] The second modified semiconductor photodetector 10 further comprises a first insulating layer 12 and a metal layer 15 stacked sequentially on the lower surface of the semiconductor substrate 11. The metal layer 15 is formed to cover the semiconductor laminate 20. The metal layer 15 may be formed to cover the lower surface of the semiconductor substrate 11, or it may be formed excluding a portion of the area so as not to interfere with the input terminal 51 of the transimpedance amplifier 50.

[0033] In the second modified semiconductor photodetector 10, the lower surface of the metal layer 15 is joined to the upper surface of the transimpedance amplifier 50. The first semiconductor electrode 24 and the second semiconductor electrode 25 are connected to the input terminal 51 of the transimpedance amplifier 50 by wires 32. Therefore, in the second modified semiconductor photodetector 10 as well, the semiconductor laminate 20 is electrically shielded by the interposed metal layer 15, preventing electromagnetic interference from the semiconductor laminate 20 from reaching the transimpedance amplifier 50. As a result, the degradation of receiving sensitivity caused by noise current due to interference is suppressed.

[0034] A second modified method for manufacturing the semiconductor photodetector 10 will now be described. On the upper surface of the semiconductor substrate 11, the deposited semiconductor laminate 20 is processed into a desired shape by wet etching or the like to form the first semiconductor electrode 24 and the second semiconductor electrode 25. On the lower surface of the semiconductor substrate 11, after forming the first insulating layer 12, a metal layer 15 is formed by vapor deposition or plating. The lower surface of the metal layer 15 is bonded to the upper surface of the transimpedance amplifier 50 with silver paste or the like. The first semiconductor electrode 24 and the second semiconductor electrode 25 and the input terminal 51 of the transimpedance amplifier 50 are then connected by wire 32.

[0035] In the first embodiment, as shown in Figures 2 and 4, the metal layer 15 is arranged such that the first insulating layer 12 is exposed in a trapezoidal shape around the first pad 13a, the second pad 14a, etc., but the embodiment is not limited to this. The metal layer 15 may be arranged to form other patterns as long as it is electrically separated from the first pad 13a, the second pad 14a, the first electrode 13, and the second electrode 14 and covers the semiconductor laminate 20 and the wiring 16.

[0036] (Second Embodiment) Figure 6 is a cross-sectional view showing a semiconductor photodetector 10 of the second embodiment. The semiconductor photodetector 10 of the second embodiment is a back-side incidence type that receives incident light 102 incident from the back surface 101. The semiconductor photodetector 10 of the second embodiment includes a semiconductor substrate 11, a semiconductor laminate 20 formed by sequentially stacking a first semiconductor layer 21 having a first conductivity type, a light absorption layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type on the upper surface of the semiconductor substrate 11, and a first insulating layer 12 formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. The semiconductor laminate 20 constitutes a PIN photodiode.

[0037] The light-absorbing layer 22 may be composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 may be composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to their respective conductivity types by introducing impurities, and the light-absorbing layer 22 may have a lower impurity concentration than the first semiconductor layer 21 and the second semiconductor layer 23.

[0038] Even if the semiconductor substrate 11 is composed of semi-insulating InP, the first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced.+ -It may be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23. The first insulator layer 12 may be composed of silicon oxide, silicon nitride, etc.

[0039] The semiconductor photodetector 10 further comprises a first electrode 13 and a second electrode 14 formed on the upper surface of a first insulator layer 12, wiring 16 connecting the first electrode 13 and the second electrode 14 to a first semiconductor electrode 24 and a second semiconductor electrode 25, respectively, and a metal layer 15 formed on the upper surface of the first insulator layer 12 so as to cover the semiconductor laminate 20 and the wiring 16, and electrically separated from the first electrode 13 and the second electrode 14. The first electrode 13 and the second electrode 14 have a cylindrical shape and extend to a predetermined depth from the upper surface of the first insulator layer 12. A first pad 13a and a second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14, respectively, to ensure a flat surface for connection. The first pad 13a and the second pad 14a may be plated. The first pad 13a and the second pad 14a are higher than the upper surface of the metal layer 15 and reach a predetermined height 103.

[0040] In the semiconductor photodetector 10 of the second embodiment, a metal layer 15 is formed on the upper surface of the first insulator layer 12, which covers the semiconductor laminate 20 and the wiring 16, and is electrically separated from the first pads 13a and 2 pads 14a and the first electrode 13 and 2 electrode 14. The metal layer 15 electromagnetically shields the semiconductor laminate 20 and the wiring 16. Furthermore, through-vias 33 are formed that penetrate the semiconductor substrate 11, the first insulator layer 12, and the metal layer 15, and the through-vias 33 are connected to the metal layer 15. The through-vias 33 protrude from the lower surface of the semiconductor substrate 11.

[0041] A method for manufacturing the semiconductor photodetector 10 according to the second embodiment will now be described. The semiconductor laminate 20 deposited on the upper surface of the semiconductor substrate 11 is processed into a desired shape by wet etching or the like to form a first semiconductor electrode 24 and a second semiconductor electrode 25 on the semiconductor laminate 20. A mirror or the like that which reflects incident light 102 may be formed on the upper surface of the semiconductor laminate 20. Next, a part of the first insulator layer 12 is formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. Furthermore, after forming the first electrode 13, the second electrode 14 and wiring 16 by plating or vapor deposition, the remaining part of the first insulator layer 12 is formed on top of them. The upper parts of the first insulator layer 12 above the first electrode 13 and the second electrode 14 are removed by dry etching or the like. Finally, a metal layer 15, a first pad 13a and a second pad 14a are formed by plating or vapor deposition. The first pad 13a and the second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14 and are higher than the upper surface of the metal layer 15. Subsequently, through holes are formed in the semiconductor substrate 11, the first insulating layer 12, and the metal layer 15 by dry etching, and metal is filled into the through holes to form through vias 33.

[0042] Figure 7 is a cross-sectional view showing the semiconductor photodetector 10 of the second embodiment mounted on the transimpedance amplifier 50. The semiconductor photodetector 10 of the second embodiment is a back-incident type that receives incident light 102 from the back surface 101, and is flip-chip mounted on the upper surface of the transimpedance amplifier 50 so that it can receive incident light 102 from above. The semiconductor photodetector 10 is inverted vertically so that its upper surface faces the upper surface of the transimpedance amplifier 50, and the first pad 13a and the second pad 14a are connected to input terminals 51 formed on the upper surface of the transimpedance amplifier 50, respectively. The connection between the first pad 13a and the second pad 14a and the input terminals 51 may be made by soldering. In addition, a through via 33 protruding from the lower surface of the semiconductor substrate 11 is connected to the ground terminal 52 of the transimpedance amplifier 50 by a wire 34.

[0043] In the second embodiment, the semiconductor photodetector 10 has a metal layer 15 formed on the upper surface of the first insulating layer 12 that covers the semiconductor laminate 20 and wiring 16. Therefore, the semiconductor laminate 20 and wiring 16 of the semiconductor photodetector 10 are electrically shielded, preventing electromagnetic interference from the semiconductor laminate 20 and wiring 16 from reaching the transimpedance amplifier 50. As a result, the deterioration of receiving sensitivity caused by noise current due to interference is suppressed, and by flip-chip mounting the semiconductor photodetector 10 on the transimpedance amplifier 50, it is possible to achieve both space saving in terms of mounting area.

[0044] Furthermore, in the semiconductor photodetector 10 of the second embodiment, the metal layer 15 is connected to the ground terminal 52 of the transimpedance amplifier 50 via through-vias 33 and wires 34. Since the metal layer 15 is maintained at ground potential, the radiation of electromagnetic waves through the metal layer 15 can be suppressed, and electromagnetic shielding of the semiconductor laminate 20 can be ensured. Moreover, in the second embodiment, by providing through-vias 33, connection by wires 34 becomes possible, making it easier to connect to other components. In addition, the connection by wires 34 is not limited to one point, but can be made to multiple locations.

[0045] Figure 8 is a cross-sectional view showing a first modified example of the semiconductor photodetector 10 of the second embodiment. The semiconductor photodetector 10 of the second embodiment is a back-incident type that receives incident light 102 from the back surface 101, and is flip-chip mounted on the upper surface of the transimpedance amplifier 50 so that it can receive incident light 102 from above. The transimpedance amplifier 50 on which the semiconductor photodetector 10 is mounted is further housed in a package 60. The semiconductor photodetector 10 is inverted vertically so that its upper surface faces the upper surface of the transimpedance amplifier 50, and the first pad 13a and the second pad 14a are connected to input terminals 51 formed on the upper surface of the transimpedance amplifier 50, respectively. The connection between the first pad 13a and the second pad 14a and the input terminals 51 may be made by soldering. In the first modified example, a through via 33 protruding from the lower surface of the semiconductor substrate 11 is connected to the ground terminal 61 of the package 60 by a wire 34.

[0046] In the first modified semiconductor photodetector 10, a metal layer 15 is formed on the upper surface of the first insulating layer 12, covering the semiconductor laminate 20 and wiring 16. Therefore, the semiconductor laminate 20 and wiring 16 of the semiconductor photodetector 10 are electrically shielded, preventing electromagnetic interference from the semiconductor laminate 20 and wiring 16 from reaching the transimpedance amplifier 50. As a result, the degradation of receiving sensitivity caused by noise current due to interference is suppressed, and by flip-chip mounting the semiconductor photodetector 10 on the transimpedance amplifier 50, it is possible to achieve both space saving in terms of mounting area.

[0047] Furthermore, in the semiconductor photodetector 10 of the first modified example, the metal layer 15 is connected to the ground terminal 61 of the package 60 via through-vias 33 and wires 34. Since the metal layer 15 is maintained at ground potential, the radiation of electromagnetic waves through the metal layer 15 can be suppressed, and electromagnetic shielding of the semiconductor laminate 20 and wiring 16 can be ensured. Moreover, in the first modified example, by providing through-vias 33, connection by wires 34 becomes possible, making it easier to connect to other components. In addition, the connection by wires 34 is not limited to one point, but can be made to multiple locations.

[0048] Figure 9 is a cross-sectional view showing a semiconductor photodetector 10 of a second modified example of the second embodiment. The semiconductor photodetector 10 of the second modified example is a surface-incident type that receives incident light 102 incident from above. The semiconductor photodetector 10 of the second modified example has a semiconductor substrate 11 and a semiconductor laminate 20 in which a first semiconductor layer 21 having a first conductivity type, a light-absorbing layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type are sequentially stacked on the upper surface of the semiconductor substrate 11. The semiconductor laminate 20 constitutes a PIN photodiode.

[0049] In the semiconductor laminate 20, the light-absorbing layer 22 is composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 are composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to have their respective conductivity types by introducing impurities, and the light-absorbing layer 22 is in a state where the impurity concentration is lower than that of the first semiconductor layer 21 and the second semiconductor layer 23.

[0050] Even if the semiconductor substrate 11 is composed of semi-insulating InP, the first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. +-It may also be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23.

[0051] The semiconductor photodetector 10 of the second modification further has a first insulating layer 12 and a metal layer 15 stacked sequentially on the lower surface of the semiconductor substrate 11. The metal layer 15 is formed to cover the semiconductor laminate 20. The metal layer 15 may be formed to cover the lower surface of the semiconductor substrate 11, or it may be formed excluding a portion of the area so as not to interfere with the input terminal 51 of the transimpedance amplifier 50. In the second modification, through vias 33 are further provided that penetrate the semiconductor substrate 11 and the first insulating layer 12. The through vias 33 are higher than the upper surface of the semiconductor substrate 11, and the lower surface of the through vias 33 is connected to the metal layer 15.

[0052] In the second modified semiconductor photodetector 10, the lower surface of the metal layer 15 is joined to the upper surface of the transimpedance amplifier 50. The first semiconductor electrode 24 and the second semiconductor electrode 25 are connected to the input terminal 51 of the transimpedance amplifier 50 by wires. Therefore, in the second modified semiconductor photodetector 10 as well, the semiconductor laminate 20 is electrically shielded by the interposed metal layer 15, preventing electromagnetic interference from the semiconductor laminate 20 from reaching the transimpedance amplifier 50. As a result, the degradation of receiving sensitivity caused by noise current due to interference is suppressed.

[0053] Furthermore, in the second modified semiconductor photodetector 10, the metal layer 15 is connected to the ground terminal 52 of the transimpedance amplifier 50 via through-vias 33 and wires 34. Since the metal layer 15 is maintained at ground potential, the radiation of electromagnetic waves through the metal layer 15 can be suppressed, and electromagnetic shielding of the semiconductor laminate 20 and wires can be ensured. Moreover, in the second modified example, by providing through-vias 33, connection by wires 34 becomes possible, making it easier to connect to other components. In addition, the connection by wires 34 is not limited to one point, but can be made to multiple locations.

[0054] A second modified method for manufacturing the semiconductor photodetector 10 will be described. On the upper surface of the semiconductor substrate 11, the deposited semiconductor laminate 20 is processed into a desired shape by wet etching or the like to form the first semiconductor electrode 24 and the second semiconductor electrode 25. On the lower surface of the semiconductor substrate 11, a first insulating layer 12 is formed, and then a metal layer 15 is formed by vapor deposition or plating. After that, through holes are formed in the semiconductor substrate 11, the first insulating layer 12, and the metal layer 15 by dry etching, and metal is filled into the through holes to form through vias 33. Furthermore, the lower surface of the metal layer 15 is joined to the upper surface of the transimpedance amplifier 50 with silver paste or the like. The first semiconductor electrode 24 and the second semiconductor electrode 25 and the input terminal 51 of the transimpedance amplifier 50 are connected by wire 32.

[0055] (Third embodiment) Figure 10 is a cross-sectional view showing the semiconductor photodetector 10 of the third embodiment mounted on the transimpedance amplifier 50. The semiconductor photodetector 10 of the third embodiment is a back-incident type that receives incident light 102 incident from the back surface 101. In Figure 10, the semiconductor photodetector 10 of the third embodiment is flip-chip mounted on the upper surface of the transimpedance amplifier 50 so that it can receive incident light 102 from above. Note that because the semiconductor photodetector 10 of the third embodiment is flip-chip mounted on the transimpedance amplifier 50, the upper surface of the semiconductor photodetector 10 is facing downwards.

[0056] The semiconductor photodetector 10 of the third embodiment includes a semiconductor substrate 11, a semiconductor laminate 20 formed by sequentially stacking a first semiconductor layer 21 having a first conductivity type, a light-absorbing layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type on the upper surface of the semiconductor substrate 11, and a first insulating layer 12 formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. The semiconductor laminate 20 constitutes a PIN photodiode.

[0057] The light-absorbing layer 22 may be composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 may be composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to their respective conductivity types by introducing impurities, and the light-absorbing layer 22 may have a lower impurity concentration than the first semiconductor layer 21 and the second semiconductor layer 23.

[0058] Even if the semiconductor substrate 11 is composed of semi-insulating InP, the first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. +-It may be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23. The first insulator layer 12 may be composed of silicon oxide, silicon nitride, etc.

[0059] The semiconductor photodetector 10 further comprises a first electrode 13 and a second electrode 14 formed on the upper surface of a first insulator layer 12, wiring 16 connecting the first electrode 13 and the second electrode 14 to a first semiconductor electrode 24 and a second semiconductor electrode 25, respectively, and a metal layer formed on the upper surface of the first insulator layer 12 so as to cover the semiconductor laminate 20 and the wiring 16, and electrically separated from the first electrode 13 and the second electrode 14. The first electrode 13 and the second electrode 14 have a cylindrical shape and extend to a predetermined depth from the upper surface of the first insulator layer 12. A first pad 13a and a second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14, respectively, to ensure a flat surface for connection. The first pad 13a and the second pad 14a may be plated. The first pad 13a and the second pad 14a are higher than the upper surface of the metal layer 15 and reach a predetermined height 103.

[0060] In the semiconductor photodetector 10 of the third embodiment, a metal layer 15 is formed on the upper surface of the first insulator layer 12, which covers the semiconductor laminate 20 and the wiring 16, and is electrically separated from the first pads 13a and 2 pads 14a and the first electrode 13 and 2 electrode 14. The metal layer 15 electromagnetically shields the semiconductor laminate 20 and the wiring 16. In addition, a pad 37 having a predetermined height is formed on the upper surface of the metal layer 15. The pad 37 may have the same height as the first pads 13a and 2 pads 14a.

[0061] The semiconductor photodetector 10 has its first pad 13a and second pad 14a connected to input terminals 51 formed on the upper surface of the transimpedance amplifier 50, respectively. Pad 37 is connected to a ground terminal 52, also formed on the upper surface of the transimpedance amplifier 50. The connections between the first pad 13a and second pad 14a and the input terminals 51, pad 37, and the ground terminal 52 may be made by soldering.

[0062] In the third embodiment, the semiconductor photodetector 10 has a metal layer 15 formed on the upper surface of the first insulating layer 12 that covers the semiconductor laminate 20 and wiring 16. Therefore, the semiconductor laminate 20 and wiring 16 of the semiconductor photodetector 10 are electrically shielded, preventing electromagnetic interference from the semiconductor laminate 20 and wiring 16 from reaching the transimpedance amplifier 50. As a result, the deterioration of receiving sensitivity caused by noise current due to interference is suppressed, and by flip-chip mounting the semiconductor photodetector 10 on the transimpedance amplifier 50, it is possible to achieve both space saving in terms of mounting area.

[0063] Furthermore, in the semiconductor photodetector 10 of the third embodiment, the metal layer 15 is connected to the ground terminal 52 of the transimpedance amplifier 50 via a pad 37. Since the metal layer 15 is maintained at ground potential, the radiation of electromagnetic waves through the metal layer 15 can be suppressed, and electromagnetic shielding of the semiconductor laminate 20 and wiring 16 can be ensured. Moreover, according to the third embodiment, since the pad 37 is formed on the upper surface of the metal layer 15, it can be easily connected by overlapping it with the ground terminal 52 of the transimpedance amplifier 50.

[0064] A method for manufacturing the semiconductor photodetector 10 according to a third embodiment will now be described. The semiconductor laminate 20 deposited on the upper surface of the semiconductor substrate 11 is processed into a desired shape by wet etching or the like to form a first semiconductor electrode 24 and a second semiconductor electrode 25 on the semiconductor laminate 20. A mirror or the like that which reflects incident light 102 may be formed on the upper surface of the semiconductor laminate 20. Next, a part of the first insulator layer 12 is formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. Furthermore, after forming the first electrode 13, the second electrode 14 and wiring 16 by plating or vapor deposition, the remaining part of the first insulator layer 12 is formed on top of them. The upper parts of the first electrode 13 and the second electrode 14 of the first insulator layer 12 are removed by dry etching or the like. A metal layer 15, a first pad 13a and a second pad 14a are formed by plating or vapor deposition. The first pad 13a and the second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14, and are higher than the upper surface of the metal layer 15. Finally, a pad 37 is formed on the upper surface of the metal layer 15 by plating, vapor deposition, or the like.

[0065] Figure 11 is a cross-sectional view showing a modified semiconductor photodetector 10 of the third embodiment. The modified semiconductor photodetector 10 is a surface-incident type that receives incident light 102 incident from above. The third modified semiconductor photodetector 10 has a semiconductor substrate 11 and a semiconductor laminate 20 in which a first semiconductor layer 21 having a first conductivity type, a light-absorbing layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type are sequentially stacked on the upper surface of the semiconductor substrate 11. The semiconductor laminate 20 constitutes a PIN photodiode.

[0066] In the semiconductor laminate 20, the light-absorbing layer 22 is composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 are composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to have their respective conductivity types by introducing impurities, and the light-absorbing layer 22 is in a state where the impurity concentration is lower than that of the first semiconductor layer 21 and the second semiconductor layer 23.

[0067] Even if the semiconductor substrate 11 is composed of semi-insulating InP, the first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. + -It may also be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23.

[0068] The modified semiconductor photodetector 10 further comprises a first insulating layer 12 and a metal layer 15 stacked sequentially on the lower surface of the semiconductor substrate 11. The metal layer 15 is formed to cover the semiconductor laminate 20. The metal layer 15 may be formed to cover the lower surface of the semiconductor substrate 11, or it may be formed excluding a portion of the area so as not to interfere with the input terminal 51 of the transimpedance amplifier 50. In the modified example, a pad 37 having a predetermined height is formed on the lower surface of the metal layer 15.

[0069] In the modified semiconductor photodetector 10, the lower surface of the metal layer 15 is joined to the upper surface of the transimpedance amplifier 50. The first semiconductor electrode 24 and the second semiconductor electrode 25 are connected to the input terminal 51 of the transimpedance amplifier 50 by wires 32. Therefore, even in the modified semiconductor photodetector 10, the semiconductor laminate 20 is electrically shielded by the interposed metal layer 15, preventing electromagnetic interference from the semiconductor laminate 20 from reaching the transimpedance amplifier 50. As a result, the degradation of receiving sensitivity caused by noise current due to interference is suppressed.

[0070] Furthermore, in the semiconductor photodetector 10 of the second embodiment, the pad 37 is connected to a ground terminal 52 formed on the upper surface of the transimpedance amplifier 50. The connection between the pad 37 and the ground terminal 52 may be made by soldering. Since the metal layer 15 is maintained at ground potential, the radiation of electromagnetic waves through the metal layer 15 can be suppressed, and electromagnetic shielding of the semiconductor laminate 20 can be ensured.

[0071] A modified method for manufacturing the semiconductor photodetector 10 will now be described. On the upper surface of the semiconductor substrate 11, the deposited semiconductor laminate 20 is processed into a desired shape by wet etching or the like to form the first semiconductor electrode 24 and the second semiconductor electrode 25. On the lower surface of the semiconductor substrate 11, after forming the first insulating layer 12, a metal layer 15 is formed by vapor deposition or plating. Furthermore, a pad 37 is formed on the upper surface of the metal layer 15 by vapor deposition or plating. The metal layer 15 is then placed so that its upper surface faces the upper surface of the transimpedance amplifier 50, and the upper surface of the pad 37 is connected to the ground terminal 52 formed on the upper surface of the transimpedance amplifier 50 with solder or the like. In addition, the first semiconductor electrode 24 and the second semiconductor electrode 25 and the input terminal 51 of the transimpedance amplifier 50 are connected by a wire 34.

[0072] (Fourth embodiment) Figure 12 is a cross-sectional view showing a semiconductor photodetector 10 of the fourth embodiment. The semiconductor photodetector 10 of the fourth embodiment is a back-side incidence type that receives incident light 102 incident from the back surface 101. The semiconductor photodetector 10 of the fourth embodiment includes a semiconductor substrate 11, a semiconductor laminate 20 formed by sequentially stacking a first semiconductor layer 21 having a first conductivity type, a light absorption layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type on the upper surface of the semiconductor substrate 11, and a first insulating layer 12A formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. The semiconductor laminate 20 constitutes a PIN photodiode.

[0073] In the semiconductor laminate 20, the light-absorbing layer 22 is composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 are composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to have their respective conductivity types by introducing impurities, and the light-absorbing layer 22 is in a state where the impurity concentration is lower than that of the first semiconductor layer 21 and the second semiconductor layer 23.

[0074] The semiconductor substrate 11 may be composed of semi-insulating InP. The first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. + -It may be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23. The first insulator layer 12A may be composed of silicon oxide, silicon nitride, etc.

[0075] The semiconductor photodetector 10 further comprises a first electrode 13 and a second electrode 14 formed on the upper surface of a first insulator layer 12, wiring 16 connecting the first electrode 13 and the second electrode 14 to a first semiconductor electrode 24 and a second semiconductor electrode 25, respectively, a metal layer 15 formed on the upper surface of the first insulator layer 12A to cover the semiconductor laminate 20 and the wiring 16, and electrically separated from the first electrode 13 and the second electrode 14, and a second insulator layer 12B covering the first insulator layer 12A and the metal layer 15. The first electrode 13 and the second electrode 14 have a cylindrical shape and extend from the upper surface of the second insulator layer 12B beyond the metal layer 15 to a predetermined depth of the first insulator layer 12A. A first pad 13a and a second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14, respectively, to ensure a flat surface for connection. The first pad 13a and the second pad 14a may be made by plating. The first pad 13a and the second pad 14a are higher than the upper surface of the second insulating layer 12B. The second insulating layer 12B may also be composed of silicon oxide, silicon nitride, or the like, similar to the first insulating layer 12A.

[0076] In the fourth embodiment, the semiconductor photodetector 10 has a metal layer 15 formed on the upper surface of the first insulating layer 12A that covers the semiconductor laminate 20 and wiring 16. Therefore, the semiconductor laminate 20 and wiring 16 of the semiconductor photodetector 10 are electrically shielded, preventing electromagnetic interference from the semiconductor laminate 20 and wiring 16 from reaching the transimpedance amplifier 50. As a result, the deterioration of receiving sensitivity caused by noise current due to interference is suppressed, and by flip-chip mounting the semiconductor photodetector 10 on the transimpedance amplifier 50, it is possible to achieve both space saving in terms of mounting area.

[0077] Furthermore, in the fourth embodiment, a second insulating layer 12B is further provided that covers the metal layer 15. The second insulating layer 12B is interposed between the transimpedance amplifier 50 and the metal layer 15 when the semiconductor photodetector 10 is flip-chip mounted on the transimpedance amplifier 50, thereby suppressing electrical interference caused by high-frequency components from the transimpedance amplifier 50 reflected by the metal layer 15.

[0078] A method for manufacturing the semiconductor photodetector 10 according to the fourth embodiment will now be described. The semiconductor laminate 20 deposited on the upper surface of the semiconductor substrate 11 is processed into a desired shape by wet etching or the like to form a first semiconductor electrode 24 and a second semiconductor electrode 25 on the semiconductor laminate 20. A mirror or the like that which reflects incident light 102 may be formed on the upper surface of the semiconductor laminate 20. Next, a part of the first insulator layer 12A is formed on the upper surface of the semiconductor substrate 11 so as to cover the semiconductor laminate 20. Furthermore, after forming the first electrode 13, the second electrode 14 and wiring 16 by plating or vapor deposition, the remaining part of the first insulator layer 12A is formed on top of them. The upper parts of the first electrode 13 and the second electrode 14 of the first insulator layer 12A are removed by dry etching or the like. A metal layer 15, a first pad 13a and a second pad 14a are formed by plating or vapor deposition. The first pad 13a and the second pad 14a are formed on the upper surfaces of the first electrode 13 and the second electrode 14, and are higher than the upper surface of the metal layer 15. Finally, a second insulating layer 12B is formed so as to cover the first insulating layer 12A and the metal layer 15.

[0079] Figure 13 is a cross-sectional view showing a modified semiconductor photodetector 10 of the fourth embodiment. The modified semiconductor photodetector 10 is a surface-incident type that receives incident light 102 incident from above. The modified semiconductor photodetector 10 has a semiconductor substrate 11 and a semiconductor laminate 20 in which a first semiconductor layer 21 having a first conductivity type, a light-absorbing layer 22 made of semiconductor, and a second semiconductor layer 23 having a second conductivity type are sequentially stacked on the upper surface of the semiconductor substrate 11. The semiconductor laminate 20 constitutes a PIN photodiode.

[0080] In the semiconductor laminate 20, the light-absorbing layer 22 is composed of a semiconductor having a bandgap energy corresponding to the wavelength of the target light. The first semiconductor layer 21 and the second semiconductor layer 23 are composed of semiconductors having a larger bandgap energy than the semiconductor constituting the light-absorbing layer 22. The first semiconductor layer 21 and the second semiconductor layer 23 are made to have their respective conductivity types by introducing impurities, and the light-absorbing layer 22 is in a state where the impurity concentration is lower than that of the first semiconductor layer 21 and the second semiconductor layer 23.

[0081] Even if the semiconductor substrate 11 is composed of semi-insulating InP, the first semiconductor layer 21 is an n-type impurity with a high concentration introduced. + -It may be composed of InP. The light absorption layer 22 may be composed of undoped InGaAs. The second semiconductor layer 23 is p in which a high concentration of p-type impurities is introduced. + -It may also be composed of InGaAsP. In these cases, the first conductivity type described above becomes n-type and the second conductivity type becomes p-type. The light absorption layer 22 and the second semiconductor layer 23 are patterned into a predetermined shape, and a part of the upper surface of the first semiconductor layer 21 is exposed, and the first semiconductor electrode 24 may be formed in this exposed region. The second semiconductor electrode 25 is formed on the upper surface of the second semiconductor layer 23.

[0082] The modified semiconductor photodetector 10 further comprises a first insulating layer 12A, a metal layer 15, and a second insulating layer 12B, which are sequentially stacked on the lower surface of the semiconductor substrate 11. The metal layer 15 is formed to cover the semiconductor laminate 20 and the wiring 16.

[0083] A modified method for manufacturing the semiconductor photodetector 10 will now be described. On the upper surface of the semiconductor substrate 11, the deposited semiconductor laminate 20 is processed into a desired shape by wet etching or the like to form the first semiconductor electrode 24 and the second semiconductor electrode 25. On the lower surface of the semiconductor substrate 11, after forming the first insulating layer 12A, a metal layer 15 is formed by vapor deposition or plating, and then the second insulating layer 12B is formed. The lower surface of the second insulating layer 12B is placed on the upper surface of the transimpedance amplifier 50. The first semiconductor electrode 24 and the second semiconductor electrode 25 and the input terminal 51 of the transimpedance amplifier 50 are connected by wire 32.

[0084] In the modified semiconductor photodetector 10, the lower surface of the metal layer 15 is mounted facing the upper surface of the transimpedance amplifier 50. The first semiconductor electrode 24 and the second semiconductor electrode 25 are connected to the input terminals of the transimpedance amplifier 50 by wires. Therefore, in the modified semiconductor photodetector 10 as well, the semiconductor laminate 20 is electrically shielded by the interposed metal layer 15, preventing electromagnetic interference from the semiconductor laminate 20 from reaching the transimpedance amplifier 50. As a result, the degradation of receiving sensitivity caused by noise current due to interference is suppressed.

[0085] Furthermore, in the modified configuration, a second insulating layer 12B is further provided, covering the metal layer 15. The second insulating layer 12B is interposed between the transimpedance amplifier 50 and the metal layer 15 when the semiconductor photodetector 10 is flip-chip mounted on the transimpedance amplifier 50, thereby suppressing electrical interference caused by high-frequency components from the transimpedance amplifier 50 reflected by the metal layer 15. [Explanation of symbols]

[0086] 11 Semiconductor substrates 12. First insulating layer 13 1st electrode 14 2nd electrode 15 metal layer 16 Wiring 20 Semiconductor Stacks 21 First Semiconductor Layer 22 Light-absorbing layer 23 Second Semiconductor Layer 50 Transimpedance Amplifier

Claims

1. A semiconductor substrate and A semiconductor laminate is formed on the upper surface of the semiconductor substrate, wherein a first semiconductor layer having a first conductivity type, a light-absorbing layer made of semiconductor, and a second semiconductor layer having a second conductivity type are sequentially stacked. A first insulating layer is formed on the upper surface of the semiconductor substrate so as to cover the semiconductor laminate, The first electrode and the second electrode formed on the upper surface of the first insulating layer, Wirings connecting the first electrode and the second electrode to the first semiconductor layer and the second semiconductor layer, respectively. A first pad and a second pad formed on the upper surfaces of the first electrode and the second electrode, respectively, A metal layer is formed on the upper surface of the first insulating layer so as to cover the semiconductor laminate and the wiring, and is electrically separated from the first electrode, the second electrode, the first pad, and the second pad. Includes, Furthermore, the first insulating layer includes a second insulating layer formed on its upper surface to cover the metal layer, and the first pad and the second pad are formed to be higher than the upper surface of the second insulating layer. Semiconductor photodetector.

2. The semiconductor photodetector according to claim 1, further comprising through vias connected to the metal layer, the semiconductor substrate, the first insulating layer, and the metal layer.

3. A semiconductor substrate and A semiconductor laminate is formed on the upper surface of the semiconductor substrate, wherein a first semiconductor layer having a first conductivity type, a light-absorbing layer made of semiconductor, and a second semiconductor layer having a second conductivity type are sequentially stacked. A first insulating layer formed to cover the lower surface of the semiconductor substrate, A metal layer is formed on the lower surface of the first insulating layer so as to cover the semiconductor laminate and the wiring connected to the semiconductor laminate, A semiconductor photodetector comprising the semiconductor substrate, a first insulating layer, and through vias penetrating the metal layer, connected to the metal layer.

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