A semiconductor photodetector chip and a method for preparing the same

Abstract

The present invention discloses a semiconductor photodetector chip and a preparation method thereof, comprising at least one photodetector unit, each photodetector unit comprising an optical coupler, a coupled optical waveguide and a micro-ring structure semiconductor lateral avalanche photodetector, the micro-ring structure semiconductor lateral avalanche photodetector comprising a silicon substrate, a silicon oxide layer, an anode contact region, a first P-type region, a ridge waveguide absorption region, a second P-type region, an avalanche region, an N-type region and a cathode contact region. The present invention is suitable for detecting and imaging weak light signals under very low absorption coefficients, and the use of a micro-ring structure does not increase the size of the device, thereby solving the problems of low detection rate and low operating speed in the prior art under weak light signals.

Description

Technical Field

[0001] The present invention relates to a chip and a preparation method thereof, in particular to a semiconductor photoelectric detector chip and a preparation method thereof, belonging to the field of photoelectric detection and sensing technology. Background Art

[0002] A photodetector is a device that converts light signals into electrical signals. If the active material of the detector has a low absorption coefficient for light of the wavelength to be detected, the length of the light absorption needs to be increased. The current solution to increase the light absorption length is mainly to use a waveguide structure. However, if the absorption coefficient is very low, in order to obtain a higher responsiveness, the waveguide structure needs to be very long, so the device size will be very large, which will increase the dark current of the device and reduce the detection rate on the one hand, and reduce the operating speed of the device on the other hand. Therefore, it is necessary to design a new photodetector chip structure to solve the defects of the existing technology when the absorption coefficient is very low. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a semiconductor photodetector chip and a preparation method thereof, which can realize high-sensitivity light detection without increasing the size of the device when the absorption coefficient of the photodetector material is very low.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A semiconductor photodetector chip, characterized in that it includes at least one photodetector unit, each photodetector unit includes an optical coupler, a coupled optical waveguide and a micro-ring structure semiconductor lateral avalanche photodetector, the incident light enters the coupled optical waveguide through the optical coupler, and then is coupled by the coupled optical waveguide into the micro-ring structure semiconductor lateral avalanche photodetector; the micro-ring structure semiconductor lateral avalanche photodetector includes a silicon substrate, a silicon oxide layer, an anode contact area, a first P-type area, a ridge waveguide absorption area, a second P-type area, an avalanche area, an N-type area and a cathode contact area, the silicon oxide layer is arranged on the upper side of the silicon substrate, the anode contact area, the first P-type area, the ridge waveguide absorption area, the second P-type area, the avalanche area, the N-type area and the cathode contact area are arranged in sequence on the upper side of the silicon oxide layer in a transverse arrangement, the first electrode is arranged on the anode contact area, and the second electrode is arranged on the cathode contact area.

[0006] Furthermore, the optical coupler is a horizontal optical coupler or a vertical optical coupler.

[0007] Furthermore, the coupling optical waveguide is made of silicon, silicon oxide or silicon nitride.

[0008] Furthermore, the micro-ring structure semiconductor lateral avalanche photodetector is a closed ring structure, and the closed ring structure includes a circular shape, an elliptical shape and an oval shape.

[0009] Furthermore, the ridge waveguide absorption region is made of a heterostructure material composed of one or more materials selected from silicon, germanium, germanium silicon and germanium quantum dots.

[0010] Furthermore, the anode contact region, the first P-type region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are made of silicon material.

[0011] Furthermore, the outer portion of the micro-ring structure semiconductor lateral avalanche photodetector is a passive waveguide.

[0012] Furthermore, the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are distributed in concentric rings.

[0013] Furthermore, the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are arranged in sequence from the inside to the outside on the upper side of the silicon oxide layer, the anode contact region and the first P-type region are located within the microring formed by the ridge waveguide absorption region, and the second P-type region, the avalanche region, the N-type region and the cathode contact region are located outside the microring formed by the ridge waveguide absorption region.

[0014] Furthermore, the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are arranged in sequence from the outside to the inside on the upper side of the silicon oxide layer, the anode contact region and the first P-type region are located outside the microring formed by the ridge waveguide absorption region, and the second P-type region, the avalanche region, the N-type region and the cathode contact region are located inside the microring formed by the ridge waveguide absorption region.

[0015] A method for preparing a semiconductor photodetector chip, characterized by comprising the following steps:

[0016] S1, take a SOI wafer, whose oxide layer thickness is 2 microns and surface silicon layer thickness is 220nm, and deposit a silicon oxide layer with a thickness of 30nm on the surface of the SOI wafer;

[0017] S2, photolithography and etching of the silicon oxide layer on the surface of the SOI wafer, etching silicon with the silicon oxide as a mask, with an etching thickness of 70 nm, forming a grating structure optical coupler, and forming an optical waveguide structure at the same time;

[0018] S3, using photoresist to protect the grating area of ​​the optical coupler, etching silicon with a thickness of 60nm, increasing the ridge height of the ridge-shaped coupling optical waveguide and the micro-ring optical waveguide from 70nm to about 130nm, and the distance between the coupling optical waveguide and the micro-ring optical waveguide in the coupling area is 250nm; then etching silicon to the buried silicon oxide in the area to be isolated to achieve isolation; the optical coupler and the ridge-shaped coupling optical waveguide are completed;

[0019] S4, from the inside of the micro-ring to the outside of the micro-ring, multiple regional ion implantation and annealing activation are performed to form different doping regions: anode contact region, first P-type region, ridge waveguide region, second P-type region, avalanche region, N-type region and cathode contact region, wherein the anode contact region is a P-type heavily doped region, the first P-type region and the second P-type region are P-type doped regions, the ridge waveguide region and the avalanche region are not doped with ion implantation, the N-type region is an N-type doped region, and the cathode contact region is an N-type heavily doped region;

[0020] S5, depositing silicon oxide, and etching silicon oxide on the ridge microring waveguide to expose an area where germanium quantum dots are to be grown epitaxially;

[0021] S6, epitaxially growing multilayer germanium quantum dots on a ridge-shaped micro-ring optical waveguide;

[0022] S7, growing a silicon dioxide passivation layer;

[0023] S8, etching silicon dioxide to expose the ohmic contact area;

[0024] S9, evaporating the ohmic contact first electrode and the second electrode;

[0025] S10. Electrode metal alloying.

[0026] Compared with the prior art, the present invention has the following advantages and effects: the semiconductor photodetector chip of the present invention comprises an optical coupler, a coupled optical waveguide and a micro-ring structure semiconductor lateral avalanche photodetector, and utilizes the micro-ring structure to achieve full absorption when the absorption coefficient of the semiconductor material is low, and performs signal multiplication through the avalanche photodetector, and adopts a lateral structure to avoid the absorption of light by the metal electrode; the chip of the present invention is suitable for the detection and imaging of weak light signals when the absorption coefficient is very low, and the use of the micro-ring structure does not increase the size of the device, thereby solving the problems of low detection rate and low operating speed under weak light signals in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a semiconductor photodetector chip of the present invention.

[0028] Figure 2 It is a schematic diagram of the micro-ring structure semiconductor lateral avalanche photodetector of the present invention.

[0029] Figure 3 It is a schematic diagram of step S1 of the preparation method of the present invention.

[0030] Figure 4 It is a schematic diagram of step S2 of the preparation method of the present invention.

[0031] Figure 5 It is a schematic diagram of step S3 of the preparation method of the present invention.

[0032] Figure 6 It is a schematic diagram of step S4 of the preparation method of the present invention.

[0033] Figure 7 It is a schematic diagram of step S5 of the preparation method of the present invention.

[0034] Figure 8 It is a schematic diagram of step S6 of the preparation method of the present invention.

[0035] Fig. 9 It is a schematic diagram of step S8 of the preparation method of the present invention. DETAILED DESCRIPTION

[0036] In order to elaborate on the technical scheme adopted by the present invention to achieve the predetermined technical purpose, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments, and the technical means or technical features in the embodiments of the present invention can be replaced without paying creative work. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0037] If a micro-ring structure photodetector is prepared, the incident light is coupled to the optical waveguide through an optical coupler, and then coupled to the micro-ring structure photodetector through the waveguide. The micro-ring structure is used to make the light circulate and be absorbed in the micro-ring, so that high responsivity and high response speed can be obtained. If the light to be detected is very weak, or even single-photon detection is required, it is a feasible solution to prepare the micro-ring structure photodetector into an avalanche photodetector. To this end, we propose a semiconductor photodetector chip, which consists of an optical coupler, a coupled optical waveguide and a micro-ring structure semiconductor lateral avalanche photodetector. The absorption area of ​​the avalanche photodetector is in the micro-ring waveguide, and the light is continuously absorbed while circulating in the micro-ring. The lateral structure can place the electrodes of the detector on both sides of the micro-ring waveguide, which can avoid the absorption of light by the electrodes. This semiconductor photodetector chip is suitable for low absorption coefficient semiconductor materials to realize the detection and imaging of weak light. The specific technical scheme is as follows:

[0038] like Figure 1 As shown, a semiconductor photodetector chip of the present invention includes at least one photodetector unit. Each photodetector unit includes an optical coupler 1, a coupled optical waveguide 2, and a micro-ring structure semiconductor lateral avalanche photodetector 3. Incident light enters the coupled optical waveguide 2 through the optical coupler 1, and then is coupled by the coupled optical waveguide 2 into the micro-ring structure semiconductor lateral avalanche photodetector 3.

[0039] like Figure 2As shown, the micro-ring structure semiconductor lateral avalanche photodetector 3 includes a silicon substrate 4, a silicon oxide layer 5, an anode contact region 6, a first P-type region 7, a ridge waveguide absorption region 8, a second P-type region 9, an avalanche region 10, an N-type region 11 and a cathode contact region 12. The silicon oxide layer 5 is arranged on the upper side of the silicon substrate 4, and the anode contact region 6, the first P-type region 7, the ridge waveguide absorption region 8, the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are sequentially arranged laterally on the upper side of the silicon oxide layer 5. The first electrode 13 is arranged on the anode contact region 6, and the second electrode 14 is arranged on the cathode contact region 12.

[0040] The optical coupler 1 is a horizontal optical coupler or a vertical optical coupler. The coupling optical waveguide 2 is made of silicon, silicon oxide or silicon nitride. The coupling optical waveguide and the micro-ring structure semiconductor lateral avalanche photodetector are located on the same horizontal plane or on different horizontal planes.

[0041] The micro-ring structure semiconductor lateral avalanche photodetector 3 is a closed ring structure, and the closed ring structure includes a circular shape, an elliptical shape and an oval shape.

[0042] The ridge waveguide absorption region 8 is a heterogeneous structure material composed of one or more materials selected from silicon, germanium, germanium silicon and germanium quantum dots. It not only serves as a ridge waveguide to realize a micro-ring structure, but also serves as an absorption region of the detector to realize absorption and detection of light.

[0043] The anode contact region 6, the first P-type region 7, the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are made of silicon material. The doping concentrations of the anode contact region 6 and the first P-type region 7 are the same or different. The doping concentrations of the avalanche region 10 and the second P-type region 9 are the same or different. The doping concentrations of the N-type region 11 and the cathode contact region 12 are the same or different.

[0044] The outer part of the micro-ring structure semiconductor lateral avalanche photodetector 3 is a passive waveguide. The micro-ring structure semiconductor lateral avalanche photodetector occupies a part of the micro-ring, and the other part of the micro-ring is a passive waveguide.

[0045] The anode contact region 6, the first P-type region 7, the ridge waveguide absorption region 8, the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are distributed in concentric annular shapes.

[0046] In one embodiment of the present invention, the anode contact region 6, the first P-type region 7, the ridge waveguide absorption region 8, the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are arranged in sequence from the inside to the outside on the upper side of the silicon oxide layer 5, the anode contact region 6 and the first P-type region 7 are located within the microring formed by the ridge waveguide absorption region 8, and the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are located outside the microring formed by the ridge waveguide absorption region 8.

[0047] In another embodiment of the present invention, the anode contact region 6, the first P-type region 7, the ridge waveguide absorption region 8, the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are arranged in sequence from the outside to the inside on the upper side of the silicon oxide layer 5, the anode contact region 6 and the first P-type region 7 are located outside the microring formed by the ridge waveguide absorption region 8, and the second P-type region 9, the avalanche region 10, the N-type region 11 and the cathode contact region 12 are located inside the microring formed by the ridge waveguide absorption region 8.

[0048] A method for preparing a semiconductor photodetector chip comprises the following steps:

[0049] S1. Take an SOI wafer, such as Figure 3 As shown, the oxide layer thickness is 2 microns, the surface silicon layer thickness is 220nm, and a silicon oxide layer with a thickness of 30nm is deposited on the surface of the SOI wafer.

[0050] S2, such as Figure 4 As shown, the silicon oxide layer on the surface of the SOI wafer is photolithographically etched and etched, and silicon is etched using the silicon oxide as a mask with an etching thickness of 70 nm to form a grating structure optical coupler and an optical waveguide structure at the same time.

[0051] S3, use photoresist to protect the optical coupler grating area, etch silicon, etch thickness 60nm, increase the ridge height of the ridge-shaped coupling optical waveguide and micro-ring optical waveguide from 70nm to about 130nm, and the distance between the coupling optical waveguide and the micro-ring optical waveguide in the coupling area is 250nm; then etch silicon to the buried silicon oxide in the area that needs to be isolated to achieve isolation; the optical coupler and ridge-shaped coupling optical waveguide are completed, and the micro-ring optical waveguide needs to be used as the basis to make a lateral avalanche photodetector with a micro-ring structure. Figure 1 As shown, a schematic diagram of the top view of the optical coupler, the ridge-shaped coupled optical waveguide and the ridge-shaped microring waveguide is formed. Figure 5 As shown, the cross-sectional structure diagram of each part.

[0052] S4, from the inside of the micro-ring to the outside of the micro-ring, multiple regional ion implantation and annealing activation are performed to form different doping regions: Figure 6As shown, the anode contact region, the first P-type region, the ridge waveguide region, the second P-type region, the avalanche region, the N-type region and the cathode contact region, wherein the anode contact region is a P-type heavily doped region, the first P-type region and the second P-type region are P-type doped regions, the ridge waveguide region and the avalanche region are not ion implanted and doped, the N-type region is an N-type doped region, and the cathode contact region is an N-type heavily doped region.

[0053] S5, such as Figure 7 As shown, silicon oxide is deposited and etched on the ridge microring waveguide to expose the area where germanium quantum dots are prepared to be epitaxially grown.

[0054] S6, such as Figure 8 As shown, multilayer germanium quantum dots are epitaxially grown on a ridge-shaped micro-ring optical waveguide.

[0055] S7. Grow a silicon dioxide passivation layer.

[0056] S8, such as Fig. 9 As shown, the silicon dioxide is etched to expose the ohmic contact area.

[0057] S9, such as Figure 2 As shown, the evaporated ohmic contacts the first electrode and the second electrode.

[0058] S10. Electrode metal alloying.

[0059] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a semiconductor photodetector chip, wherein the semiconductor photodetector chip comprises at least one photodetector unit, each photodetector unit comprises an optical coupler, a coupled optical waveguide and a micro-ring structure semiconductor lateral avalanche photodetector, wherein incident light enters the coupled optical waveguide through the optical coupler, and then is coupled by the coupled optical waveguide into the micro-ring structure semiconductor lateral avalanche photodetector; the micro-ring structure semiconductor lateral avalanche photodetector comprises a silicon substrate, a silicon oxide layer, an anode contact region, a first P-type region, a ridge waveguide absorption region, a second P-type region, an avalanche region, an N-type region and a cathode contact region, wherein the silicon oxide layer is provided On the upper side of the silicon substrate, the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are arranged in sequence on the upper side of the silicon oxide layer, the first electrode is arranged on the anode contact region, and the second electrode is arranged on the cathode contact region; the optical coupler adopts a horizontal optical coupler or a vertical optical coupler; the coupled optical waveguide is made of silicon, silicon oxide or silicon nitride; the micro-ring structure semiconductor lateral avalanche photodetector is a closed ring structure, and the closed ring structure includes a circular, elliptical or oval shape; the ridge waveguide absorption region adopts silicon, germanium, germanium silicon or the like. and germanium quantum dots; the anode contact region, the first P-type region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are made of silicon material; the outer part of the micro-ring structure semiconductor lateral avalanche photodetector is a passive waveguide; the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are arranged in a concentric annular shape; the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are arranged in sequence from inside to outside on the silicon oxide layer On the upper side, the anode contact region and the first P-type region are located in the area inside the micro-ring formed by the ridge waveguide absorption region, and the second P-type region, the avalanche region, the N-type region and the cathode contact region are located outside the micro-ring formed by the ridge waveguide absorption region; the anode contact region, the first P-type region, the ridge waveguide absorption region, the second P-type region, the avalanche region, the N-type region and the cathode contact region are arranged in sequence from outside to inside on the upper side of the silicon oxide layer, the anode contact region and the first P-type region are located outside the micro-ring formed by the ridge waveguide absorption region, and the second P-type region, the avalanche region, the N-type region and the cathode contact region are located inside the micro-ring formed by the ridge waveguide absorption region; Features The following steps are involved: S1, take a SOI wafer, whose oxide layer thickness is 2 microns and surface silicon layer thickness is 220nm, and deposit a silicon oxide layer with a thickness of 30nm on the surface of the SOI wafer; S2, photolithography and etching of the silicon oxide layer on the surface of the SOI wafer, etching silicon with the silicon oxide as a mask, with an etching thickness of 70 nm, forming a grating structure optical coupler, and forming an optical waveguide structure at the same time; S3, using photoresist to protect the grating area of ​​the optical coupler, etching silicon, etching thickness of 60nm, increasing the ridge height of the ridge-shaped coupling optical waveguide and the micro-ring optical waveguide from 70nm to 130nm, and the distance between the coupling optical waveguide and the micro-ring optical waveguide in the coupling area is 250nm; then etching silicon to the buried silicon oxide in the area to be isolated to achieve isolation; the optical coupler and the ridge-shaped coupling optical waveguide are completed; S4, from the inside of the micro-ring to the outside of the micro-ring, multiple regional ion implantation and annealing activation are performed to form different doping regions: anode contact region, first P-type region, ridge waveguide region, second P-type region, avalanche region, N-type region and cathode contact region, wherein the anode contact region is a P-type heavily doped region, the first P-type region and the second P-type region are P-type doped regions, the ridge waveguide region and the avalanche region are not doped with ion implantation, the N-type region is an N-type doped region, and the cathode contact region is an N-type heavily doped region; S5, depositing silicon oxide, and etching silicon oxide on the ridge microring waveguide to expose an area where germanium quantum dots are to be grown epitaxially; S6, epitaxially growing multilayer germanium quantum dots on a ridge-shaped micro-ring optical waveguide; S7, growing a silicon dioxide passivation layer; S8, etching silicon dioxide to expose the ohmic contact area; S9, evaporating the ohmic contact first electrode and the second electrode; S10. Electrode metal alloying.

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