CN112397594A - Photoelectric detector and manufacturing method thereof - Google Patents

Abstract

The invention relates to the technical field of semiconductor integrated circuits, and provides a photodetector and a manufacturing method thereof. The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a specified distance from the outer ring of the annular p+ diffusion area; the resistance area includes a resistance and an R pole, wherein the two ends of the resistance are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used for Connect the pin VAPD for supplying power to the photodetector; the N pole of the photodetector is also used to connect the first capacitor, and the other end of the first capacitor is grounded, so as to filter the input power supply signal of the pin VAPD. The invention solves the problem that the optical receiving sensitivity of the 10G access terminal equipment is significantly deteriorated due to the crosstalk of the 5G WiFi.

Description

Photodetector and method of making the same

【Technical field】

The present invention relates to the technical field of semiconductor integrated circuits, in particular to a photodetector and a manufacturing method thereof.

【Background technique】

With the popularization and application of broadband services such as e-commerce, 4K/8K video, Internet of Things, and cloud computing, as well as ultra-broadband applications such as unmanned intelligent driving, virtual reality (VR), artificial intelligence (AI), and smart cities The gradual rise of services will vigorously encourage operators, Internet companies and other companies to actively upgrade their existing network equipment to meet the requirements of emerging services for ultra-broadband, ultra-large capacity, and low latency.

For example, in terms of access network, over the past 20 years, technological innovations from telephone line access (Kbps rate) to copper line access (Mbps rate) to optical fiber access (Gbps) have been realized, and the bandwidth of home users has been improved. The rate was increased from the original Kbps to Gbps. At present, China has basically completed the deployment of gigabit-rate GPON/EPON access networks, and has entered the stage of large-scale commercial deployment of 10G-GON/10G-EPON.

In terms of development and deployment to 10G-GON/10G-EPON home terminal optical modem and other equipment, due to business requirements, optical modem equipment needs to support both optical fiber access and wireless WiFi access, resulting in the development of terminal equipment. The technical difficulties of coexisting with wireless signals. The main reason is that in order to achieve indoor transmission and coverage of 5G WiFi, its signal strength needs to reach 24dBm to 30dBm. The electromagnetic signal of such intensity is easy to crosstalk to the optoelectronic signal port in the terminal optical modem module, which seriously affects the receiving sensitivity of the optoelectronic signal, resulting in that the receiving sensitivity cannot meet the standard specification requirements.

In view of this, overcoming the defects existing in the prior art is an urgent problem to be solved in the technical field.

[Content of the Invention]

The technical problem to be solved by the embodiments of the present invention is that in order to meet the development requirements of services, the access terminal equipment needs to support both optical fiber access and wireless WiFi access connection modes. When the WiFi access standard is upgraded from 2.4G WiFi to 5G WiFi with a higher transmission rate, in order to meet the transmission distance requirement covering the home, the 5G WiFi signal strength is also increased to 24dBm to 30dBm. The working frequency band of the 5G WiFi signal is just within the working frequency range of the 10G photoelectric signal, which causes the 5G WiFi signal to cause serious electromagnetic crosstalk to the 10G photoelectric signal, which significantly degrades the receiving sensitivity of the photoelectric signal, resulting in the optical signal of the terminal equipment. The access sensitivity cannot meet the standard requirements.

In a first aspect, the present invention discloses a photodetector, including a photodetector area and a resistance area, specifically:

The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a position different from the outer ring of the annular p+ diffusion area by a specified distance;

The resistance area includes a resistor and an R pole, wherein the two ends of the resistor are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used to connect the pin VAPD that supplies power to the photodetector; the N pole of the photodetector is also After connecting the first capacitor, the other end of the first capacitor is grounded, so as to filter the input power supply signal of the pin VAPD.

Preferably, the resistor is a polysilicon resistor; wherein, the polysilicon resistor is grown in a designated area of the oxide layer in the photodetector, and is located on the P electrode contact layer of the photodetector; wherein, the polysilicon resistor and The P-contact layers of the photodetector are separated by the oxide layer; or,

The resistance is an n-well resistance, and the n-well resistance is formed in a designated area of the photodetector by n-type doping before the oxide layer is formed in the photodetector;

Among them, the two sides of the polysilicon resistor or the n-well resistor are respectively doped by n+ implantation to make two n+ contact regions of the polysilicon resistor or the n-well resistor; the n+ contact regions are respectively used for connecting with the R pole and the N pole of the photodetector. connect.

Preferably, the resistance value of the polysilicon resistor is set between 10 ohms and 500 ohms, the thickness of the polysilicon layer of the corresponding polysilicon resistor is 1-3um, the resistivity of the doped polysilicon is 100±10Ω.um, and its length and width are Then set it according to the shape characteristics of the photodetector and the resistance value to be formed.

Preferably, the depth of the n-well resistor is 0.5um-1.5um, the resistivity of the n-well is 50±10Ω.um, and its length and width are set according to the shape characteristics of the photodetector and the size of the resistance to be formed.

In a second aspect, the present invention discloses a photodetector, comprising a photodetector area, a resistance area and a capacitance area, specifically:

The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a position different from the outer ring of the annular p+ diffusion area by a specified distance;

The resistance area includes a resistor and an R pole, wherein the two ends of the resistor are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used to connect the pin VAPD that supplies power to the photodetector; the N pole of the photodetector is also For connecting the capacitive area;

The capacitor region includes a built-in capacitor and a GND pole, wherein one end of the built-in capacitor is connected to the N pole, and the other end of the built-in capacitor is connected to the GND pole, so as to filter the input power supply signal of the pin VAPD.

Preferably, the built-in capacitor is made of a metal-insulator-metal structure, including a first layer of metal material, an intermediate insulating layer material and a second layer of metal material, wherein the first layer of metal material is located on the intermediate insulating layer material and the second layer of metal material Bottom of metal material, specific:

When forming the two electrodes of the built-in capacitor, the first electrode is in contact with the epitaxial portion of the first layer of metal material through n+ implantation doping, wherein the intermediate insulation is not grown on the epitaxial portion of the first layer of metal material layer material and second layer metal material;

The second electrode is a designated area on the second layer of metal material, and the designated area is respectively located on both sides of the second electrode relative to the first electrode.

Preferably, the first layer of metal material and the second layer of metal material are one metal material or multiple metal mixed materials among Al, Cu, Au, W, Co and Ti; the material of the intermediate insulating layer: SiO ₂ , with a thickness of 5-10nm, the relative dielectric constant is 3.9±0.5; the capacitance per unit area of the metal-insulator-metal structure is 2-4fF/um ² .

In a third aspect, the present invention also discloses a method for manufacturing a photodetector, the method comprising:

growing a first oxide layer on the p+ contact layer;

growing a polysilicon layer on the first oxide layer, exposing and etching the area reserved for making polysilicon resistors;

growing oxide on the etched area, so that the formed second oxide layer covers the polysilicon layer;

Perform n+ implantation doping at both ends of the polysilicon resistance region to make two resistance contact regions of the polysilicon resistance;

Etch the area where the electrode needs to be drawn out until the p+ contact area and the n+ contact area on the surface, forming a contact hole for epitaxial growth of the metal electrode material;

Epitaxially growing electrode materials to form P, N and R electrodes of the photodetector;

For the light-receiving area of the photodetector, the oxide layer on the surface is etched away to the p+ contact layer on the surface, forming a window for effectively receiving external light signals.

Preferably, before forming the p+ contact layer, the method includes:

Process the InP substrate wafer; perform n+ doping on the InP substrate to form a n+InP contact layer for making the N pole of the photodetector; epitaxially grow an n-InGaAsP layer; epitaxially grow a p layer -InGaAsP layer; an InP layer is epitaxially grown; p+ doping is performed on the InP layer to form a p+InP contact layer for making the P pole of the photodetector; deep n+ implantation doping is performed to form a The n+ contact area connected with the n+InP contact layer is used to make the N pole of the photodetector on the surface of the n+ contact area; wherein, the p+ contact layer is specifically a p+InP contact layer; or,

Process the Si substrate wafer; perform n+ doping on the Si substrate to form a n+Si contact layer for making the N pole of the photodetector; epitaxially grow an intrinsic Si layer; epitaxially grow an n layer type Si, forming a buffer layer together with the intrinsic Si layer; epitaxial growth of an intrinsic Si avalanche layer for generating avalanche effect and avalanche amplification of photogenerated electrons; epitaxial growth of a p-type Si charge layer; epitaxial growth A layer of intrinsic Ge absorption layer is used to absorb optical signals and generate photogenerated electrons and holes; p+ doping is performed by injection to form a p+ contact area on the surface of the intrinsic Ge absorption layer, which is used to make the P electrode of the photodetector ; Carry out deep n+ implantation doping to form an n+ contact region communicating with the n+Si contact layer, for making the N pole of the photodetector on the surface; wherein, the p+ contact layer is specifically a p+Ge contact layer .

In a fourth aspect, the present invention also discloses a method for fabricating a photodetector. Before fabricating the oxide layer, the method includes:

Implant n-type dopant in the designated area to form an n-well resistance region;

Perform n+ implantation doping at both ends of the n-well resistance region to make two n+ contact regions of the n-well resistance;

The area of the lead-out electrode is etched until the p+ contact area and the n+ contact area on the surface are formed to form contact holes for epitaxial growth of metal electrode materials;

Epitaxially growing electrode materials to form P, N and R electrodes of the photodetector;

For the light-receiving area of the photodetector, the oxide layer on the surface is etched to form a window for effectively receiving external light signals.

Compared with the prior art, the beneficial effects of the embodiments of the present invention are:

The photodetector proposed by the present invention incorporates a resistor structure, or a combined structure of resistors and capacitors. This resistor forms a low-pass filter with an external capacitor on the path that supplies power to the photodetector, or is directly connected to the photodetector. The combined structure of the resistor and capacitor constitutes a low-pass filter, which can effectively filter out the 5G WiFi crosstalk signal, and solve the problem that the optical receiving sensitivity of the 10G access terminal equipment is significantly deteriorated due to the 5G WiFi crosstalk.

[Description of drawings]

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a top view of a photodetector packaging structure in the prior art provided by the present invention;

FIG. 2 is a schematic top view of the structure of a photodetector with integrated resistance provided by an embodiment of the present invention;

3 is a top view of a photodetector packaging structure according to an embodiment of the present invention;

4 is a schematic top view of the structure of a photodetector with integrated resistors and metal regions according to an embodiment of the present invention;

5 is a schematic top view of the structure of a photodetector with integrated resistance and capacitance provided by an embodiment of the present invention;

6 is a schematic flowchart of a method for manufacturing a photodetector according to an embodiment of the present invention;

7 is a schematic diagram corresponding to the structure shown in FIG. 2 and a combination of cross-sectional views corresponding to section line 1 and section line 2 in an InP-based APD structure using a polysilicon resistor provided by an embodiment of the present invention;

8 is a schematic diagram of a combination of cross-sectional views corresponding to section line 1 and section line 2 corresponding to the structure shown in FIG. 2 in a SiGe APD structure using polysilicon resistors provided by an embodiment of the present invention;

FIG. 9 is a schematic flowchart of another method for manufacturing a photodetector according to an embodiment of the present invention;

10 is a schematic diagram corresponding to the structure shown in FIG. 2 and a combination of cross-sectional views corresponding to section line 1 and section line 2 in an InP-based APD structure using an n-well resistor provided by an embodiment of the present invention;

11 is a schematic diagram of a combination of cross-sectional views corresponding to section line 1 and section line 2 in an InP-based APD structure using an n-well resistor provided by an embodiment of the present invention, which corresponds to the structure shown in FIG. 2 and has a metal region;

12 is a schematic diagram corresponding to the structure shown in FIG. 2 in a SiGe APD structure using an n-well resistor provided by an embodiment of the present invention and a combination of cross-sectional views corresponding to section line 1 and section line 2;

13 is a schematic diagram of a combination of cross-sectional views corresponding to section line 1 and section line 2 in a SiGe APD structure using an n-well resistor provided by an embodiment of the present invention, which corresponds to the structure shown in FIG. 2 and has a metal region;

FIG. 14 is a simulation result diagram of the filtering effect of the WiFi signal by the photodetector of the present invention.

【Detailed ways】

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the description of the present invention, the orientation or positional relationship indicated by the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc. are based on the drawings The orientation or positional relationship shown is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

The inventor found through research that the current 10G ONU optical modem will add filter resistors and capacitors on the branch circuit that supplies power to the photodetector on the PCB board, and also add filter capacitors inside the light receiving component. However, the current filtering scheme cannot effectively filter out the WiFi crosstalk signal on the pin VAPD of the light-receiving optical component.

Filter resistors and capacitors added to the branch on the PCB for powering the photodetector: the WiFi signal on the VAPD pin of the light-receiving optical component cannot be filtered out, because the WiFi crosstalk signal enters directly through the VAPD pin (the VAPD pin equivalent to an antenna).

The filter bandwidth formed by the VAPD pin (the parasitic resistance of which is about tens of milliohms) and the internal filter capacitor (usually 470pF) of the light-receiving component is on the order of GHz, and it cannot filter out the WiFi crosstalk signal.

The current 10G ONU optical modem test results are:

When there is no 5G WiFi signal, the optical receiving sensitivity of the 10G ONU optical modem test is about -29～-31dBm@BER=1E-3, where dBm is the unit of incident optical power, assuming that the incident optical power is Pin milliwatts (mW) , then the incident optical power after the unit is changed to dBm is 10*log(Pin/1); BER=1E-3 means that the bit error rate is equal to 1E-3.

After the 5G WiFi signal is turned on, the optical receiving sensitivity of the 10G ONU optical modem test degrades to less than -20dBm@BER=1E-3.

The technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Embodiment 1:

Embodiment 1 of the present invention provides a photodetector, as shown in FIG. 2 , including a photodetector area and a resistance area, specifically:

The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a position different from the outer ring of the annular p+ diffusion area by a specified distance;

The resistance area includes a resistor and an R pole, wherein the two ends of the resistor are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used to connect the pin VAPD that supplies power to the photodetector; the N pole of the photodetector is also After connecting the first capacitor, the other end of the first capacitor is grounded, so as to filter the input power supply signal of the pin VAPD.

The photodetector proposed in the embodiment of the present invention incorporates a resistor structure, and the resistor forms a low-pass filter with an external capacitor on the path that supplies power to the photodetector, so as to achieve the purpose of effectively filtering out 5G WiFi crosstalk signals and solve the problem of The problem that the optical reception sensitivity of 10G access terminal equipment is significantly degraded due to 5G WiFi crosstalk. As shown in FIG. 3 , it is a schematic diagram showing the connection of the pin structure of the TO-CAN package realized in combination with the photodetector chip proposed in the embodiment of the present invention.

In the embodiment of the present invention, at least two feasible ways for experimental demonstration are provided for the above-mentioned resistance implementation.

method one:

The resistor is a polysilicon resistor; wherein, the polysilicon resistor is grown in a designated area of the oxide layer in the photodetector, and is located on the P electrode contact layer of the photodetector; wherein, the polysilicon resistor is connected to the photodetector. The P electrode contact layers are separated by the oxide layer.

In the background technology scenario proposed by the embodiment of the present invention, the resistance value of the polysilicon resistor is set between 10 ohms and 500 ohms, the thickness of the polysilicon layer of the corresponding polysilicon resistor is 1-3um, and the resistivity of the doped polysilicon is 1-3um. 100±10Ω.um, and its length and width are set according to the shape characteristics of the photodetector and the resistance value to be formed. The specific calculation method of polysilicon resistance value is given here, as follows:

Assuming that the thickness of the polysilicon resistance layer is d, the resistivity of the polysilicon resistance layer is ρ (unit is Ω.um), and the length and width of the polysilicon resistance are L microns (um) and W microns (um), respectively, then the polysilicon resistance layer is The resistance value of the square resistor is:

R _square =ρ/d(Ω.um ² );

Note: Sheet resistance refers to a resistor whose length and width are both 1um.

The resistance value of the polysilicon resistor is:

R=R _square ×L/W(Ω);

For the resistivity ρ, it is generally obtained by a four-probe square resistivity tester. It is also possible to measure the size and resistance value of the resistor under test, and then calculate the resistivity according to the calculation formula: (1) first measure the size of the resistor under test, including the length L and the area S of the cross section; (2) use a high-precision electrical (3) Calculate the _resistivity according to the resistivity formula, as follows:

ρ=R _S ×S/L;

In order to simplify the measurement process, the length L and width W of the resistance to be measured are made equal in design, and the thickness of the resistance to be measured is d, then the resistivity calculation formula of the resistance to be measured is:

ρ= _RS ×(W×d)/L= _RS ×d;

That is to say, for the measured resistance with the same length L and width W, its resistivity can be simplified to be obtained by multiplying its measured resistance value and thickness.

In the embodiment of the present invention, a set of parameter examples are given: polysilicon layer thickness: 2um; doped polysilicon resistivity: 100Ω.um (according to the above resistivity measurement method and experimental results: if P-type doping is used, the doping The concentration is about 9.6E+18; if N-type doping is used, the doping concentration is about 5E+17); polysilicon sheet resistance: 50Ω; 500 ohm polysilicon resistor size example: width 30um*length 300um; Example: width 200um*length 40um.

As shown in FIG. 4 , it is an improved solution proposed by the embodiment of the present invention, wherein the polysilicon resistor is covered with a metal layer connected to the N pole of the resistor (marked as metal in the top view shown in FIG. 4 ) region), the metal layer material is the same as the electrode material of the resistor and the photodetector, which is Al, Cu, Au, W (tungsten), Co (cobalt) and Ti (titanium) and other metal materials; the metal layer region and the resistance The distances between the P pole, the half-moon annular n+ diffusion region and the upper boundary of the device are all 10-20um; the metal layer and the device substrate (usually connected to the ground by default) form a capacitor, and the dielectric between the metal layer and the device substrate forms a capacitor. The electrical material is SiO ₂ , and its relative permittivity is 3.9±0.5; assuming that the thickness of SiO ₂ is 15-30 nm, the capacitance per unit area of the metal-substrate structure is 0.67-1.33 fF/um ² ; if this metal The width of the layer is 60um and the length is 300um, and the parasitic capacitance formed by the metal layer and the substrate is about 12-24pF. Among them, the capacitance calculation formula of the metal layer-substrate structure is:

C=ε ₀ ×ε _SiO2 ×S/d;

In the above formula, ε ₀ is the vacuum dielectric constant, and its value is 8.854×10 ^-12 (F/m); ε _SiO2 is the relative dielectric constant of the SiO ₂ material; S is the area of the metal layer-substrate structure capacitance, This is equal to the width of the metal layer-substrate structure capacitor multiplied by the length of the metal layer-substrate structure capacitor, and the area of the capacitor per unit area is 1um ² ; d is the thickness of the dielectric material (here, SiO ₂ ).

The polysilicon resistor and the capacitor formed by the metal layer above it and the device substrate form a low-pass filter, which can filter out part of the alien crosstalk signal in advance to a certain extent (the attenuation degree of the alien crosstalk signal is about dozens of times); Then, combined with an external capacitor, the alien crosstalk signal is further effectively filtered out.

Method two:

The resistance is an n-well resistance, and the n-well resistance is formed in a designated area of the photodetector by n-type doping before the oxide layer is formed in the photodetector;

Among them, the two sides of the polysilicon resistor or the n-well resistor are respectively doped by n+ implantation to make two n+ contact regions of the polysilicon resistor or the n-well resistor; the n+ contact regions are respectively used for connecting with the R pole and the N pole of the photodetector. connect.

In the background technology scenario proposed by the embodiment of the present invention, the depth of the n-well resistor is 0.5um-1.5um, the resistivity of the n-well is 50±10Ω.um, and its length and width are based on the shape characteristics of the photodetector, and the size of the resistance to be formed.

Example 2:

An embodiment of the present invention proposes a photodetector. Compared with the photodetector in Embodiment 1, which integrates a built-in resistor, the photodetector in Embodiment 1 also needs to connect a peripheral capacitor at the N pole to form a filter circuit. , and in Embodiment 2 of the present invention, the peripheral capacitors that need to be added during the use of Embodiment 1 are further integrated into the photodetector, as shown in Figure 5, including the photodetector area, the resistance area and the capacitance area, specific:

The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a position different from the outer ring of the annular p+ diffusion area by a specified distance;

The resistance area includes a resistor and an R pole, wherein the two ends of the resistor are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used to connect the pin VAPD that supplies power to the photodetector; the N pole of the photodetector is also For connecting the capacitive area;

The capacitor region includes a built-in capacitor and a GND pole, wherein one end of the built-in capacitor is connected to the N pole, and the other end of the built-in capacitor is connected to the GND pole, so as to filter the input power supply signal of the pin VAPD.

The combined structure of the resistor and the capacitor in the photodetector proposed in the embodiment of the present invention directly forms the low-pass filter by the combined structure of the resistor and the capacitor in the photodetector, so as to achieve the purpose of effectively filtering out the 5G WiFi crosstalk signal, and solve the problem of 10G WiFi. The problem that the optical reception sensitivity of the access terminal equipment is significantly degraded due to 5G WiFi crosstalk.

In the embodiment of the present invention, the built-in capacitor is made of a metal-insulator-metal structure, including a first layer of metal material, an intermediate insulating layer material and a second layer of metal material, wherein the first layer of metal material is located in the intermediate insulating layer material and the bottom of the second layer of metal material, specifically:

When forming the two electrodes of the built-in capacitor, the first electrode is in contact with the epitaxial portion of the first layer of metal material through n+ implantation doping, wherein the intermediate insulation is not grown on the epitaxial portion of the first layer of metal material layer material and second layer metal material;

The second electrode is a designated area on the second layer of metal material, and the designated area is respectively located on both sides of the second electrode relative to the first electrode.

For example: the metal material of the first layer and the metal material of the second layer are all metal materials such as Al, Cu, Au, W (tungsten), Co (cobalt) and Ti (titanium); the material of the intermediate insulating layer is SiO ₂ with a thickness of 5 -10nm, the relative dielectric constant is 3.9±0.5; the capacitance per unit area of the metal-insulator-metal structure is 2-4fF/um ² . Through experimental demonstration, the resistance value in the photodetector is 500 ohms, and the filter capacitor is 50-100pF, which is more suitable for ONU optical modems in optical access networks such as 10G-GON/10G-EPON and next-generation 50G PON and other optoelectronics. Application scenarios that coexist with WiFi signals; the light receiving component using this photodetector structure can effectively filter out WiFi signals before WiFi signals enter the signal end of the photodetector through radiation crosstalk, so as to prevent WiFi signals from being mixed into the photodetector. In the useful data signal, the sensitivity of the light receiving component is prevented from being degraded by the WiFi signal.

It should be noted that the significance of the embodiment of the present invention lies in that both the resistor and the capacitor are built into the chip itself. Therefore, relatively speaking, the technical details described in Embodiment 1 for the built-in resistor part are also applicable to the embodiment of the present invention.

Example 3:

An embodiment of the present invention provides a method for fabricating a photodetector, as shown in FIG. 6 , the method includes:

In step 201, a first oxide layer is grown on the p+ contact layer.

In step 202, a polysilicon layer is grown on the first oxide layer, and a region reserved for making polysilicon resistors is exposed and etched.

In step 203, an oxide is grown on the etched area, so that the second oxide layer formed covers the polysilicon layer.

In step 204, n+ implantation and doping are performed on both ends of the polysilicon resistor region to form two resistive contact regions of the polysilicon resistor.

In step 205, etching is performed on the region where the electrode needs to be drawn out until the p+ contact region and the n+ contact region on the surface are formed, and a contact hole for epitaxial growth of the metal electrode material is formed.

In step 206, electrode material is epitaxially grown to form electrodes P, N and R electrodes of the photodetector and a metal layer above the resistance region.

In step 207, on the light receiving area of the photodetector, the oxide layer on the surface is etched away to the p+ contact layer on the surface to form a window for effectively receiving external light signals.

In the embodiment of the present invention, in different photodetector chip fabrication scenarios, the corresponding p+ contact layer will also appear as different material layers. Two cases are listed as follows:

Case 1:

A schematic diagram of the structure of an InP (Indium Phosphorus) APD integrated with polysilicon resistors, as shown in Figure 7, and with reference to the top view shown in Figure 2, including an InP substrate, an n+InP contact layer, and n-InGaAsP (Indium Gallium Arsenide Phosphorus) , p-InGaAsP, p+InP contact layer, oxide layer, polysilicon layer and metal layer. Among them, the InP substrate, n+InP contact layer, n-InGaAsP (indium gallium arsenide phosphorus), p-InGaAsP, p+InP contact layer form a SiGe APD structure, which is used to convert the input optical signal into a photo-generated current signal; polysilicon The layer constitutes a polysilicon resistor, and its function is to form a low-pass filter with the capacitor to effectively filter out the external crosstalk signal.

Then, before forming the p+ contact layer, the method includes:

Process the InP substrate wafer; perform n+ doping on the InP substrate to form a n+InP contact layer for making the N pole of the photodetector; epitaxially grow an n-InGaAsP layer; epitaxially grow a p layer -InGaAsP layer; an InP layer is epitaxially grown; p+ doping is performed on the InP layer to form a p+InP contact layer for making the P pole of the photodetector; deep n+ implantation doping is performed to form a The n+ contact area connected with the n+InP contact layer is used to make the N pole of the photodetector on the surface of the n+ contact area; at this time, the p+ contact layer is specifically the p+InP contact layer.

As a result, an InP APD structure is fabricated, in which n-InGaAsP and p-InGaAsP form a PN junction; under the action of an external electric field, the photogenerated electrons generated in the PN junction region will enter the n-InGaAsP layer, n+InP contacts layer, and enters the surface through the n+ contact area fabricated in step 7 and flows into the N pole; the photogenerated holes generated in the PN junction area will enter the p+ contact area and flow into the P pole.

As shown in FIG. 11 , in order to learn from the corresponding structural cross-sectional view after the metal area structure is added in Example 1, by comparing the difference between FIG. 11 and FIG. The metal region structure is obtained by further etching and growing.

Case two:

A schematic structural diagram of a SiGe (silicon germanium) APD (avalanche photodetector) integrated with polysilicon resistors, as shown in FIG. 8, and referring to the top view shown in FIG. 2, including a Si substrate, an n+ contact layer, an intrinsic Si layer, n-type Si layer, intrinsic Si avalanche layer, p-type Si charge layer, intrinsic Ge absorber layer, p+Ge contact layer, oxide layer, polysilicon layer and metal layer. Among them, Si substrate, n+ contact layer, intrinsic Si layer, n-type Si layer, intrinsic Si avalanche layer, p-type Si charge layer, intrinsic Ge absorption layer and p+Ge contact layer constitute the SiGeAPD structure, and its function is to The input optical signal is converted into a photo-generated current signal; the polysilicon layer constitutes a polysilicon resistor, and its function is to form a low-pass filter with the capacitor to effectively filter out the external crosstalk signal.

Then, before forming the p+ contact layer, the method includes:

Process the Si substrate wafer; perform n+ doping on the Si substrate to form a n+Si contact layer for making the N pole of the photodetector; epitaxially grow an intrinsic Si layer; epitaxially grow an n layer type Si, forming a buffer layer together with the intrinsic Si layer; epitaxial growth of an intrinsic Si avalanche layer for generating avalanche effect and avalanche amplification of photogenerated electrons; epitaxial growth of a p-type Si charge layer; epitaxial growth A layer of intrinsic Ge absorption layer is used to absorb optical signals and generate photogenerated electrons and holes; p+ doping is performed by injection to form a p+ contact area on the surface of the intrinsic Ge absorption layer, which is used to make the P electrode of the photodetector ; Carry out deep n+ implantation doping to form an n+ contact region connected to the n+Si contact layer, which is used to make the N pole of the photodetector on the surface; at this time, the p+ contact layer is specifically a p+Ge contact Floor.

As a result, a SiGe APD structure is fabricated, in which the p-type Si charge layer forms a PN junction with the intrinsic Si avalanche layer and n-type Si; under the action of an external electric field, the photogenerated electrons generated by the intrinsic Ge absorption layer will enter the The p-type Si charge layer, the intrinsic Si avalanche layer, the n-type Si, the intrinsic Si layer and the n+Si contact layer enter the surface through the n+ contact region fabricated in step 9 and flow into the N pole; intrinsic Ge absorbs The photogenerated holes generated by the layer will enter the p+ contact region and flow into the p pole.

As shown in FIG. 13 , in order to learn from the corresponding structural cross-sectional view after the metal area structure is added in Example 1, by comparing the differences between FIG. 11 and FIG. The metal region structure is obtained by further etching and growing.

Example 4:

An embodiment of the present invention provides a method for fabricating a photodetector. Before fabricating an oxide layer, as shown in FIG. 9 , referring to the cross-sectional view of the structure shown in FIG. 10 , the method includes:

In step 301, an n-type dopant is implanted in a designated region to form an n-well resistance region.

In step 302, n+ implantation and doping are performed on both ends of the n-well resistance region to form two n+ contact regions of the n-well resistance region.

In step 303, the region of the lead-out electrode is etched until the p+ contact region and the n+ contact region on the surface are formed to form contact holes for epitaxial growth of the metal electrode material.

In step 304, electrode materials are epitaxially grown to form electrodes P, N and R electrodes of the photodetector.

In step 305, the oxide layer on the surface of the photodetector is etched away to form a window for effectively receiving external light signals.

As shown in FIG. 12, it is a schematic structural diagram of a SiGe (silicon germanium) APD (avalanche photodetector) with an integrated n-well resistor proposed by the present invention, including a Si substrate, an n+ contact layer, an intrinsic Si layer, and an n-type Si layer. layer, intrinsic Si avalanche layer, p-type Si charge layer, intrinsic Ge absorber layer, p+Ge contact layer, n-well, oxide layer and metal layer. Among them, Si substrate, n+ contact layer, intrinsic Si layer, n-type Si layer, intrinsic Si avalanche layer, p-type Si charge layer, intrinsic Ge absorption layer and p+Ge contact layer constitute the SiGe APD structure. It converts the input optical signal into a photo-generated current signal; the n-well area constitutes an n-well resistor, and its function is to form a low-pass filter with the capacitor to effectively filter out the external crosstalk signal.

The photodetector processing steps shown in FIG. 12 will be described in detail below.

Step 1: Process Si substrate wafer;

Step 2: do n+ doping on the Si substrate to form a n+Si contact layer, which is used to make the N pole of the photodetector;

Step 3: Epitaxial growth of an intrinsic Si layer;

Step 4: A layer of n-type Si is epitaxially grown to form a buffer layer together with the intrinsic Si layer in Step 3;

Step 5: epitaxially grow a layer of intrinsic Si avalanche layer to generate avalanche effect, avalanche amplification of photogenerated electrons, to achieve the purpose of improving photoresponsivity;

Step 6: Epitaxial growth of a p-type Si charge layer;

Step 7: Epitaxial growth of an intrinsic Ge absorber layer for absorbing optical signals and generating photogenerated electrons and holes;

Step 8: Implantation for p+ doping, forming a p+ contact area on the surface of the intrinsic Ge absorption layer, which is used to make the P pole of the photodetector;

Step 9: Carry out deep n+ implantation doping to form an n+ contact area connected to the n+Si contact layer of step 2, which is used to facilitate the fabrication of the N pole of the photodetector on the surface;

Steps 1 to 9 fabricated the SiGe APD structure, in which the p-type Si charge layer forms a PN junction with the intrinsic Si avalanche layer and n-type Si; under the action of the external electric field, the intrinsic Ge absorber layer produces The photogenerated electrons will enter the p-type Si charge layer, the intrinsic Si avalanche layer, the n-type Si, the intrinsic Si layer and the n+Si contact layer, and enter the surface through the n+ contact area fabricated in step 9, and flow into the N pole; The photogenerated holes generated by the intrinsic Ge absorbing layer will enter the p+ contact region and flow into the P electrode;

Step 10: Implant n-type dopant to form an n-well resistance region;

Step 11: Perform n+ implantation doping at both ends of the n-well resistor region to make two n+ contact regions of the n-well resistor;

Step 12: Etch the area where the electrode needs to be drawn out until the surface p+ contact area and n+ contact area are formed to form contact holes for epitaxial growth of metal electrode materials;

Step 13: Epitaxially growing electrode material Au-Sn or other metal electrode materials to form electrodes P, N and R of the photodetector.

Step 14: For the light-receiving area of the photodetector, the oxide layer on the surface is etched away to the p+Ge contact layer on the surface to form a window for effectively receiving external light signals.

As shown in FIG. 14 , it is a simulation result diagram of the filtering effect of the WiFi signal by the photodetector of the present invention, wherein the resistance value in the photodetector is 100 ohms, and the filter capacitance is 470pF. The simulation results show that the 2.4G WiFi crosstalk signal can be attenuated by about 57dB (that is, the 2.4G WiFi crosstalk signal is attenuated to about 1/708), and the 5G WiFi crosstalk signal can be attenuated by about 63.3dB (that is, the 2.4G WiFi crosstalk signal is attenuated to about 1/708). The signal is attenuated to about 1/1462).

It is worth noting that the information exchange and execution process between the modules and units in the above-mentioned device and the system are based on the same concept as the processing method embodiments of the present invention. For details, please refer to the descriptions in the method embodiments of the present invention. , will not be repeated here.

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium can include: Read memory (ROM, Read Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk, etc.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. a photodetector, is characterized in that, comprises photodetector area and resistance area, concrete: The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a position different from the outer ring of the annular p+ diffusion area by a specified distance; The resistance area includes a resistor and an R pole, wherein the two ends of the resistor are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used to connect the pin VAPD that supplies power to the photodetector; the N pole of the photodetector is also After connecting the first capacitor, the other end of the first capacitor is grounded, so as to filter the input power supply signal of the pin VAPD. 2 . The photodetector according to claim 1 , wherein the resistor is a polysilicon resistor; wherein, the polysilicon resistor is grown in a designated area of the oxide layer in the photodetector, and is located on the side of the photodetector. 3 . On the P electrode contact layer; wherein, the polysilicon resistor and the P electrode contact layer of the photodetector are separated by the oxide layer; or, The resistance is an n-well resistance, and the n-well resistance is formed in a designated area of the photodetector by n-type doping before the oxide layer is formed in the photodetector; Among them, the two sides of the polysilicon resistor or the n-well resistor are respectively doped with n+ implantation to make two n+ contact regions of the polysilicon resistor or the n-well resistor; the n+ contact regions are respectively used for connecting with the R pole and the N pole of the photodetector. connect. 3 . The photodetector according to claim 2 , wherein the resistance value of the polysilicon resistor is set between 10 ohms and 500 ohms, the thickness of the polysilicon layer of the corresponding polysilicon resistor is 1-3um, and the doping The resistivity of polysilicon is 100±10Ω.um, and its length and width are set according to the shape characteristics of the photodetector and the resistance value to be formed. 4. The photodetector according to claim 2, wherein the depth of the n-well resistor is 0.5um-1.5um, the resistivity of the n-well is 50±10Ω.um, and its length and width are based on the photodetector The shape characteristics of the device and the size of the resistance value to be formed are set. 5. A photodetector, characterized in that, comprising a photodetector area, a resistance area and a capacitance area, specifically: The photodetector area includes a half-moon annular n+ diffusion area connected to the N pole, an annular p+ diffusion area connected to the P pole, and a light-receiving area; wherein, the light-receiving area is located in the ring cavity of the annular p+ diffusion area, and the half-moon annular n+ The diffusion area is set at a position different from the outer ring of the annular p+ diffusion area by a specified distance; The resistance area includes a resistor and an R pole, wherein the two ends of the resistor are respectively connected to the R pole and the N pole of the photodetector; wherein, the R pole is used to connect the pin VAPD that supplies power to the photodetector; the N pole of the photodetector is also For connecting the capacitive area; The capacitor region includes a built-in capacitor and a GND pole, wherein one end of the built-in capacitor is connected to the N pole, and the other end of the built-in capacitor is connected to the GND pole, so as to filter the input power supply signal of the pin VAPD. 6. The photodetector according to claim 5, wherein the built-in capacitor is made of a metal-insulator-metal structure, comprising a first layer of metal material, an intermediate insulating layer material and a second layer of metal material, wherein the first layer of A layer of metal material is located at the bottom of the intermediate insulating layer material and the second layer of metal material, specifically: When forming the two electrodes of the built-in capacitor, the first electrode is in contact with the epitaxial portion of the first layer of metal material through n+ implantation doping, wherein the intermediate insulation is not grown on the epitaxial portion of the first layer of metal material layer material and second layer metal material; The second electrode is a designated area on the second layer of metal material, and the designated area is respectively located on both sides of the second electrode relative to the first electrode. 7 . The photodetector according to claim 6 , wherein the first layer of metal material and the second layer of metal material are one or more of Al, Cu, Au, W, Co and Ti. 8 . Metal mixed material; intermediate insulating layer material: SiO ₂ , with a thickness of 5-10 nm and a relative permittivity of 3.9±0.5; the metal-insulator-metal structure has a capacitance per unit area of 2-4fF/um ² . 8. A method of making a photodetector, wherein the method comprises: growing a first oxide layer on the p+ contact layer; growing a polysilicon layer on the first oxide layer, exposing and etching the area reserved for making polysilicon resistors; growing oxide on the etched area, so that the formed second oxide layer covers the polysilicon layer; Perform n+ implantation doping at both ends of the polysilicon resistance region to make two resistance contact regions of the polysilicon resistance; Etch the area where the electrode needs to be drawn out until the p+ contact area and the n+ contact area on the surface, forming a contact hole for epitaxial growth of the metal electrode material; Epitaxially growing electrode materials to form P, N and R electrodes of the photodetector; For the light-receiving area of the photodetector, the oxide layer on the surface is etched away to the p+ contact layer on the surface, forming a window for effectively receiving external light signals. 9. The method for fabricating a photodetector according to claim 8, wherein before forming the p+ contact layer, the method comprises: Process the InP substrate wafer; perform n+ doping on the InP substrate to form a n+InP contact layer for making the N pole of the photodetector; epitaxially grow an n-InGaAsP layer; epitaxially grow a p layer -InGaAsP layer; an InP layer is epitaxially grown; p+ doping is performed on the InP layer to form a p+InP contact layer for making the P pole of the photodetector; deep n+ implantation doping is performed to form a The n+ contact area connected by the n+InP contact layer is used to make the N pole of the photodetector on the surface of the n+ contact area; wherein, the p+ contact layer is specifically a p+InP contact layer; or, Process the Si substrate wafer; perform n+ doping on the Si substrate to form a n+Si contact layer for making the N pole of the photodetector; epitaxially grow an intrinsic Si layer; epitaxially grow an n layer type Si, forming a buffer layer together with the intrinsic Si layer; epitaxial growth of an intrinsic Si avalanche layer for generating avalanche effect and avalanche amplification of photogenerated electrons; epitaxial growth of a p-type Si charge layer; epitaxial growth A layer of intrinsic Ge absorption layer is used to absorb optical signals and generate photogenerated electrons and holes; p+ doping is performed by injection to form a p+ contact area on the surface of the intrinsic Ge absorption layer, which is used to make the P electrode of the photodetector ; Carry out deep n+ implantation doping to form an n+ contact region communicating with the n+Si contact layer, for making the N pole of the photodetector on the surface; wherein, the p+ contact layer is specifically a p+Ge contact layer . 10. A method for fabricating a photodetector, characterized in that, before fabricating the oxide layer, the method comprises: Implant n-type dopant in the designated area to form an n-well resistance region; Perform n+ implantation doping at both ends of the n-well resistance region to make two n+ contact regions of the n-well resistance; The area of the lead-out electrode is etched until the p+ contact area and the n+ contact area on the surface are formed to form contact holes for epitaxial growth of metal electrode materials; Epitaxially growing electrode materials to form P, N and R electrodes of the photodetector; For the light-receiving area of the photodetector, the oxide layer on the surface is etched to form a window for effectively receiving external light signals.

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